GB2322973A

GB2322973A - Shielding case for electronic equipment

Info

Publication number: GB2322973A
Application number: GB9802797A
Authority: GB
Inventors: Nobuyuki Suzuki; Kiminori Terashima
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1997-03-07
Filing date: 1998-02-11
Publication date: 1998-09-09
Anticipated expiration: 2018-02-11
Also published as: KR19980079965A; GB2322973B; JPH10256768A; DE19809725C2; CN1101128C; CN1195265A; DE19809725A1; MY118826A; GB9802797D0

Abstract

In the shielding case of the present invention, a circuit component and a connector are mounted on a circuit board (6), and the circuit board is mounted in a metal frame (3) having upper and lower openings (1,2). A lower cover (8) for covering the lower opening has an approximately rectangular flat portion and an engaging piece bent in an L-section on the peripheral edge thereof. In a specific position of the flat portion is an anti-deflection piece (16) which is formed by bending approximately squarely. The flat portion of the lower cover is attached on the underside of the metal frame and the engaging piece is elastically attached on the side wall of the metal frame. When the lower cover is attached to the lower opening of the metal frame, the forward end of the anti-deflection piece is disposed oppositely to an insulating layer (17) coated on the surface of the circuit board, and strengthens the cover against inward deflation towards the circuitry on the circuit board.

Description

2322973 SHIELDING CASE FOR ELECTRONIC EQUIPMENT The present invention

relates to a shielding case for electronic equipment which uses a high-frequency circuit such as a tuner for a television receiver.

Generally, in a shielding case produced of a conductive metal, a circuit board with an oscillation circuit is mounted to reduce unnecessary radiation to the outside and also a circuit board with a high-gain highfrequency amplifier is mounted to prevent entrance of noise from other circuits or from outside.

Figs. 3 and 4 show this type of conventional shielding case; Fig. 3 is an exploded perspective bottom view of the shielding case, and Fig. 4 is a s(ctional view of the shielding case. The shielding case shown 1.n these f igures is comprised primarily of a rectangular metal frame 3 provided with openings 1 and 2 in the upper and lower sections, a circuit board 6 attached within the metal frame 3 and mounted with a circuit component 4 and a connector 5, and an upper cover 7 and a lower cover 8 attached to the openings 1 and 2 of the metal frame 3 respectively.

The upper cover 7 has a flat portion 9 formed in an approximately rectangular shape to cover the opening 1 of the metal frame 3. The f lat portion 9 is arranged in parallel with the circuit board 6. On the peripheral edge of the upper cover 7 is formed an engaging piece 10 which is bent squarely into an L-section towards the metal frame 3. Similarly, the lower cover 8 has a flat portion 11 formed in an approximately rectangular shape to cover the opening 2 of the metal frame 3; the flat portion 11 being arranged in parallel with the circuit board 6. On the peripheral edge of the upper cover 8 is formed an engaging piece 12 which is bent squarely into an L-section towards the metal frame 3. In one end of the lower cover 8 is formed a cutout 13 into which an unillustrated counterpart connector to be connected to the connector 5 is inserted.

In assembling the shielding case thus constituted, the circuit board 6 is f irs t inserted into the metal frame 3 through the upper opening 1 or the lower opening 2; then the f lat portion 9 of the upper cover 7 is set on the upper side of the metal frame 3, the engaging piece 10 is elastically fitted to the side wall of the metal frame 3, to thereby attach the upper cover 7 to the upper opening 1 of the metal frame 3. Similarly, with the flat portion 11 of the lower cover 8 set on the lower side of the metal frame 3, the engaging piece 12 is elastically 2 fitted to the side wall of the metal frame 3 to attach the lower cover 8 to the lower opening 2 of the metal frame 3. After the assembling of the shielding case, the lower cover 8 side of the shielding case is set on an unillustrated circuit board, and then the attaching sections 14 and 15 provided at the end of the metal frame 3 are attached to the circuit board.

In the conventional shielding case described above the engaging pieces 10 and 12 of the upper cover 7 and the lower cover 8 are elastically attaching to the side wall of the metal frame 3, thereby enabling attaching the covers 7 and 8 to the openings 1 and 2 of the metal frame 3. At this time, however, a reaction force from the metal frame 3 tends to act on the engaging pieces 10 and 12, producing a bending moment in a direction in which the flat portions 9 and 11 of the upper cover 7 and the lower cover 8 will come close to the circuit board 6, consequently deflecting inwards the flat portions 9 and 11 of the upper cover 7 and the lower cover 8 into contact with the circuit component 4 mounted on the circuit board. Particularly when there is form(-d a cutout 13 in a part of the flat portion 11, the rigidity of the flat portion 11 will decrease in the vicinity of the cutout 13, making the aforementioned problem more noticeable. A similar problem will occur also when there is a short spacing between the covers 7 and 8 and the circuit board 6.

3 1 In view of the above-described problem inherent in the heretofore known device, it is an object of the present invention to -provide a shielding case, in which an antideflection piece is formed, by bending nearly squarely, in a flat portion of a cover covering an opening of a metal frame, and the forward end of the anti-deflection piece disposed on the opposite side of the surface of the circuit board. With the provision of such an anti-deflection piece, the antideflection piece contacts the surface of the circuit board when a bending moment acts on the flat portion of the cover in a direction in which the flat portion comes close to the circuit board inside, thereby supporting the f lat portion to prevent deflection and deformation of the flat portion. Even when the flat portion of the cover has a little rigidity, or when the spacing between the cover and the circuit board is short, the flat portion of the cover can reliably be prevented from contacting a circuit component on the circuit board.

The shielding case for electronic equipment of the present invention includes a metal frame having an opening, a circuit board housed in the metal frame, and a cover attached at the opening of the metal frame. And the cover is provided at the flat portion with an antideflection piece formed by bending approximately squarely and the forward end of the antideflection piece is set oppositely to.the surface of the 4 circuit board.

In the shielding case of the aforesaid constitution, when the forward end of the anti-deflection piece is in contact with the surface of the circuit board, a comiDressive force acts on the anti-deflection piece in a direction perpendicular to the board surface. Since the anti-deflection piece has great rigidity against the force in this direction, the bending moment acting on the flat portion of the cover will be received by the anti-def lection piece. The quantity and location of the anti-deflection piece can be selected according to the shape of the cover. For example, when the flat portion is partly cut out, it is desirable that the antideflection piece be formed in the vicinity of the cutout. When no cutout is formed in the flat portion, it is advised that the anti-deflection piece be f ormed near the center of the f lat portion where the f lat portion deflects to a maximum.

The forward end of the anti-def lection piece may be held in direct contact with the surface of the circuit board. If, in this case, an insulating coating is applied to, or an insulating film is affixed on, the surface of the circuit board disposed on the opposite side of the forward end of the anti-deflection piece, the forward e'nd of the anti- deflection piece will contact the surface of the insulating layer, but will not directly contact the surface of the circuit board when a bending moment acts on the cover; therefore it is possible to arrange a wiring pattern for circuit components on the surface of the circuit board in relation to the forward end of the anti-deflection piece, thereby enhancing the freedom of circuit design.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is an exploded bottom view, in perspective, of one embodiment of a shielding case for electronic equipment according to the present invention; Fig. 2 is a sectional view of the shielding case; Fig. 3 is an exploded bottom view, in perspective, of a conventional shielding case for electronic equipment; and Fig. 4 is a sectional view of the conventional shielding case.

An embodiment of a shielding case according to the present invention will be explained with reference to the accompanying drawings. Fig. 1 is an exploded bottom view, in perspective, of one embodiment of the shielding case for electronic equipment according to the present invention; and Fig. 2 is a sectional view of the shielding case. In these drawings, the same members as those in Figs. 3 and 4 are designated by the same reference numerals.

As shown in Figs. 1 and 2, the shielding case of the present h6 embodiment is different from the conventional example shown in Figs. 3 and 4 in the respects that an anti-deflection piece 16 is formed in a predetermined position on a flat portion 11 of a lower cover 8, for instance in the vicinity of a cutout 13, and that an insulating layer 17 is coated on the surface of a circuit board 6 disposed on the opposite side of the forward end of the anti-deflection piece 16. The shielding case is basically the same in other points of constitution.

The anti-deflection piece 16 is formed by cutting and bending squarely inwards a part of the flat portion 11 of the lower cover 8. Then, with the lower cover 8 attached to a lower opening 2 of a metal frame 3 as shown in Fig. 2, an engaging piece 12 of the lower cover 8 is engaged from outside with the side wall of the metal frame 3. In this state, the forward end of the anti -de f lection piece 16 faces the surface of the circuit board 6; the surface of the circuit board 6 is coated in this part with the insulating layer 17.

In the shielding case of such constitution, when the lower cover 8 is attached to the lower opening 2 of the metal frame 3, a reaction force from the metal frame 3 acts on the engaging piece 12 which engages from outside with the side wall of the metal frame 3. Therefore, when a bending moment acts on the flat portion 11 of the lower cover 8 in a. direction in which the anti-deflection piece 16 approaches the circuit board 6, the forward end of the anti-deflection piece 16 contacts the h7 insulating layer 17 coated on the circuit board 6. At this time, the compressive force acts on the anti-def lection piece 16 in a direction perpendicular to the board surface. The antideflection piece 16, having great rigidity, will not be deformed with a force in this direction. The bending moment exerted to the flat portion 11 of the lower cover 8 is received by the anti- deflection piece 16. Therefore, if the rigidity of the f lat portion 11 of the lower cover 8 has decreased because of the formation of the cutout 13 in the flat portion, the deflection of the flat portion 11 can be prevented by the anti-deflection piece 16 and accordingly the flat portion is prevented from contacting the circuit components on the circuit board.

In the embodiment described above, the shielding cover with the circuit board 6 coated with the insulating layer 17 on the surface disposed on the opposite side of the forward end of the anti-deflection piece 16 has been described. When no wiring pattern is present in the position disposed on the opposite side of the forward end of the an-Li-deflection piece 16, the insulating layer 17 can be safely dispensed with.

Furthermore, in the above-described embodiment, the anti-deflection piece 16 is formed in the flat portion 11 of the lower cover. It should be noticed, however, that the present invention is not limited thereto and a similar anti-deflection piece may be formed also in the flat portion h8 9 of the upper cover 7 when needed- 09

Claims

1. A shielding case for electronic equipment, comprising: a metal frame having an opening, a circuit board mounted in said metal frame, and a cover attached to an opening of said metal frame; said cover having on a flat portion an antideflection piece which is bent approximately squarely; and said anti-def lection piece being disposed with a f orward end thereof disposed on the opposite side of the surface of said circuit board.

2. A shielding case for electronic equipment according to claim 1, wherein an insulating layer is coated on the surface of said circuit board disposed on the opposite side of the forward end of said anti- deflection piece.

3. A shielding case substantially as hereinbefore described with reference to, and as illustrated by, any of Figures 1 and 2 of the accompanying drawings.

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