Inductor devices – With supporting and/or spacing means between coil and core – Coil clamps or wedges
Reexamination Certificate
2000-06-14
2001-12-04
Mai, Anh (Department: 2832)
Inductor devices
With supporting and/or spacing means between coil and core
Coil clamps or wedges
C336S210000
Reexamination Certificate
active
06326875
ABSTRACT:
FIELD OF THE INVENTION
This invention is generally related to inductive circuits implemented on a printed board, such as planar transformers, wherein ferrite pieces are used which are secured around a wire pattern formed on the circuit board. A route for the magnetic flux is brought about by these pieces. More specifically, the invention concerns attachment of such pieces to a circuit board.
BACKGROUND OF THE INVENTION
Planar magnetics is an advantageous alternative to the conventional iron cores, when a low profile is desired for inductive components. This alternative has been used generally, e.g. when implementing transformers on a circuit board.
In these so-called planar transformers, the transformer coils are integrated on the printed board. Such a structure is illustrated in
FIG. 1
, which shows four conductive layers A to D of a multiple layer circuit board PCB, whereby the desired winding pattern WP
1
. . . WP
4
is implemented for each layer. Together, these winding patterns form the transformer windings (primary and secondary windings). The transformer core in the case shown as an example in the figure is formed by E-profiled ferrite pieces F
1
and F
2
, for which the circuit board has corresponding openings H
1
. . . H
3
extending through the board at the arms of the E. The ferrite pieces are pushed into the openings from opposite sides of the circuit board, whereby they will be placed opposite to one another at the openings so that the end surfaces of the E's arms are against each other.
Conventionally, the ferrite couple has been secured to the circuit board by gluing, so that one ferrite piece is first glued to the circuit board and then the ferrite pieces are glued together. However, gluing is a work step generally perceived as a health hazard, even despite the fact that efficient suction fans are used in the working space. Another drawback of gluing is that, once glued together, it is impossible later to remove the ferrite pieces without damaging the circuit board.
Another known method of securing ferrite pieces is to lock them to one another with the aid of a suitable mechanical locking body. Such a locking method is illustrated in
FIG. 2
, which is a cross-sectional view of ferrite pieces secured to one another and to a circuit board. The mechanical locking body CL
1
attaching the ferrite pieces to each other is formed by a spring-like metal strip, which is pushed through the openings (H
1
, H
3
) in the circuit board so that it is located around the ferrite pieces. The metal strip functions as a spring pressing the ferrite pieces against each other (this pressing function of the spring is indicated by arrows P in the figure). In
FIG. 2
only the upper ferrite piece F
1
is E-profiled, whereas the lower piece F
2
is slab-like.
By using only a mechanical locking body the drawbacks caused by gluing are avoided. However, attaching by using only a mechanical attaching body has the drawback that in certain operating environments the ferrite pieces can rub against the circuit board. This may have the result that the protective coating of the circuit board wears off and the ferrite piece contacts and damages the conductive pattern on the circuit board. Such an operating environment where vibration occurs can be e.g. in means of transportation, e.g. in trains or street-cars.
SUMMARY OF THE INVENTION
It is a purpose of the invention to eliminate the drawbacks mentioned above and to bring about an arrangement with which the above-mentioned gluing step can be entirely eliminated from the circuit board's manufacture step and with which, in addition, wear of the circuit board is avoided also in such operating environments where the circuit board is affected by vibration and can thus vibrate.
This aim is achieved through the solution defined in the independent claims.
The idea of the invention is to form such spring-like protrusions in the ends of the ferrite couple clamp, which are formed so in relation to openings in the circuit board that when the clamp is put in its place, they are pressed against the edges of openings in the circuit board, thereby locking the ferrite couple in position in relation to the circuit board.
The spring-like clamp according to the invention implements two functions: it holds the ferrite pieces locked to one another and at the same time it holds the ferrite couple locked in relation to the circuit board so that it can not move in relation to the circuit board, even if the circuit board is affected by vibration in its operating environment.
Since gluing is no longer needed, the ferrite pieces can be removed or exchanged without damaging the circuit board.
It is an additional advantage of the solution according to the invention that it is suitable for an automatic manufacturing process, because the clamp may be put in position mechanically in connection with the automatic assembling process of the other circuit board components.
REFERENCES:
patent: 4704592 (1987-11-01), Marth et al.
patent: 4967175 (1990-10-01), Berg et al.
patent: 6033594 (2000-03-01), Enokido et al.
patent: 3620762 A1 (1987-12-01), None
patent: 3807892 A1 (1989-09-01), None
patent: 0060933 (1977-05-01), None
patent: 02-0298005 (1990-12-01), None
patent: 5-55048 A (1993-03-01), None
patent: 40-6112046 (1994-04-01), None
patent: 06132146 A (1994-05-01), None
International Search report for PCT/FI98/00970.
Altera Law Group LLC
Mai Anh
Nokia Networks Oy
LandOfFree
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