Inductor devices – Winding formed of plural coils – Two windings
Reexamination Certificate
2000-03-29
2001-07-17
Easthom, Karl D. (Department: 2832)
Inductor devices
Winding formed of plural coils
Two windings
C336S198000
Reexamination Certificate
active
06262650
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to coil transformers, and in particular, to a coil former for coil transformers.
PROBLEM
In the art of coil transformers there exists a need for a coil former for a certain class of multi-layer coil transformers. Coil transformers typically include a pair of “E” shaped ferrite transformer cores (E-cores), a plastic housing, and a coil. The E-cores have a center leg and two outer legs equally spaced apart. The E-core legs are configured in a facial relationship with the coil wound around the center legs. The coil leads are soldered onto metallic pins molded into the plastic housing. The metallic pins are used to mount the coil transformer on a printed circuit (PC) board by either a through hole mount or a surface mount.
The plastic housing is a two piece housing, with a first piece connected around the exterior edge of one of the E-cores and a second piece connected around the exterior edge of the other E-core. In a typical assembly, a metallic clip connects around one end of the housing to fasten the housing pieces and E-cores in the facial relationship. A bonding agent such as glue, is used on the opposite end between abutting faces of the outer legs of the E-cores to form a completed coil transformer. In other examples, the clip is replaced by a bonding agent between abutting faces of both pairs of outer legs.
In the transformer art, alignment of the E-core legs during assembly is critical because transformer inductance is directly proportional to the contact between the cross section of the legs. Transformer performance is also affected by air gaps induced by the bonding agent or glue between abutting faces of the E-core legs.
Recent improvements in the art of coil transformers have led to the development of a new transformer E-core that incorporates the PC board mounting apparatuses into the E-cores. These new E-cores allow a stacked mounting configuration of two transformers on a PC board. These new transformers are known as multi-layer coil transformers as described in U.S. Pat. No. 5,861,790.
SOLUTION
The present invention advances the art by providing a coil-former for multi-layer coil transformers. A first advantage of the present coil former is that it provides a form to wind the transformer coil to construct a multi-layer coil transformer. A second advantage of the present coil former is that it provides a means for connecting and aligning the transformer E-cores during assembly to produce a substantially homogeneous transformer core without the use of bonding agents or clips. The substantially homogeneous transformer core is especially advantageous in that it yields improved inductance capabilities over prior art transformers. A third advantage of the present coil former is that it provides a means for connecting the coil leads to the homogeneous transformer core without interfering with the stackable configuration of the multi-layer coil transformers. A fourth advantage of the present coil former is that in some examples the coil former may also provide the connecting apparatus for mounting the transformer to a PC board. This is especially advantageous because it permits the use of the present coil former to construct both non-stackable transformers similar to prior art transformers and multi-layer transformers, both of which have improved inductance characteristics.
The coil former comprises a rectangular casing with a central interior cavity formed through the casing. The casing includes a pair of channels integrally formed and circumscribing the outer diameter of the casing in perpendicular orientation with respect to the cavity. A first plurality of metallic pins connected perpendicular to the casing in parallel orientation with the cavity connect the E-cores to form the homogeneous transformer core. The metallic pins also provide an electrical link for connecting the coil leads to the transformer core.
In a first example of the coil former, the case includes a pair of flanges integrally formed along a first and second edge to align the E-cores during assembly. In another example of the coil former, the case includes a second pair of flanges integrally formed along a third and fourth edge to add improved alignment and add additional structural integrity to the assembled coil transformer. In another example of the coil former, the second pair of flanges includes a plurality of metallic pins for additional structural integrity. In another example of the coil former, the flanges include flared ends to provide additional structural integrity to the assembled coil transformer. In another example of the coil former, a second plurality of metallic pins are connected to the casing in a perpendicular relationship to the first plurality of metallic pins to connect a non-stackable transformer core to a PC board.
REFERENCES:
patent: 3668586 (1972-06-01), Horbach
patent: 3939450 (1976-02-01), Donnelly
patent: 4117588 (1978-10-01), Johnson
patent: 4454554 (1984-06-01), Coleman
patent: 4758808 (1988-07-01), Sasaki et al.
patent: 4916424 (1990-04-01), Kijima
patent: 5396211 (1995-03-01), Noguchi et al.
patent: 5534839 (1996-07-01), Mackin et al.
patent: 5861790 (1999-01-01), Johnson, Jr. et al.
Avaya Technology Corporation
Duft, Graziano & Forest, P.C.
Easthom Karl D.
Lee Richard K.
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