Double sided gasket

Details Double sided gasket Double sided gasket

1999-09-20

2001-12-25

Knight, Anthony (Department: 3626)

Seal for a joint or juncture

Seal between fixed parts or static contact against...

Contact seal for other than internal combustion engine, or...

C277S650000, C277S920000, C277S649000, C174S034000, C174S034000, C174S0170CT, C267S036100, C267S041000

Reexamination Certificate

active

06332618

ABSTRACT:

BACKGROUND
The present invention relates to gaskets which prevent leakage of radio frequency signals when mounting shielded radio electronics. Specifically, such gaskets can be used to achieve a safe connection between a shielding box and a printed circuit board (PCB) in devices such as radio telephones.
In order to prevent the leakage of radio frequency signals between components of radio electronics devices, a gasket must ensure good contact between the surfaces of the two mounted components. Adequate contact requires that the distance between contact points should be less than or approximately equal to a predetermined ratio (e.g., 1/20th) of the wavelength of the radio frequency to be shielded. As the radio frequency increases, the wavelength decreases. Therefore, effective shielding of high radio frequencies requires a shorter distance between adjacent contact points than low radio frequencies. Because the surface of one or both of the components can be rough or uneven, it is desirable that the gasket include flexible extensions such as spring arms which contact the adjacent component at finite contact points. A gasket having a flat or inflexible contact surface is likely to allow large or difficult to predict distances between contact points with an adjacent component surface.
One conventional gasket design
20
is shown in
FIGS. 9 and 10
. This gasket
20
includes a plurality of spring arms
22
. Each spring arm
22
has one free end
24
which projects out of one side of a gasket body
26
. A component which is mounted adjacent to that side of the gasket body
26
is, at minimum, contacted at areas separated by a contact distance D. Each spring arm
22
is stamped out of the gasket body
26
, and therefore has a thickness T
1
equivalent to a thickness T
2
of the gasket body
26
. As a result, if a low spring constant, and therefore thin spring arm
22
is desired, the gasket body
26
itself must be equally as thin. A disadvantage of this design is that the thinner the gasket body
26
, the more difficult the gasket body
26
is to mount and assemble. A second disadvantage of this design is that the side of the gasket body
26
opposite the side from which spring arms
22
project presents a generally flat surface
28
to one of the components between which the gasket
20
is mounted. The flat surface
28
does not ensure known contact points with a component adjacent the flat surface
28
. Absent known contact points, the shielding effect of the gasket
20
can be compromised if the component adjacent the flat surface
28
of the gasket has a rough or uneven surface, causing the gasket to have contact gaps greater in length than the wavelength of the radio frequency to be shielded.
FIGS. 11 and 12
show a conventional gasket
30
of similar construction to the gasket
20
shown in
FIGS. 9 and 10
. However, gasket
30
has spring arms
32
each having a thickness T
3
smaller than the thickness T
4
of the gasket body
34
. This arrangement is achieved by etching the spring arm
32
into the metal material which forms the gasket
30
. Nonetheless, this configuration still presents a flat surface
36
to one of two components between which the gasket
30
is mounted.
The conventional gasket
40
shown in
FIGS. 13 and 14
attempts to solve the problem of indefinite contact points inherent in a flat gasket surface by alternating downwardly projecting spring arms
42
and upwardly projecting spring arms
44
. However, this configuration requires that for a given length spring arm L, the distance between contact points D
1
on a component surface is about twice the length L. This design makes it difficult to maintain both a long spring arm, which has a long travel or tolerance for roughness or unevenness in a component surface, and a minimum small distance between adjacent contact points on the component surface adjacent the gasket
40
. In addition, this design requires two bending steps (one to form the upwardly projecting spring arms
44
and one to form the downwardly projecting the spring arms
42
) to form the gasket
40
, making such a gasket difficult to manufacture.
Accordingly, a need exists for a gasket that includes spring arms that project from opposite sides of a gasket body
26
, while still providing at least one set of long spring arms having low spring constants and maintaining proportionally small distances between adjacent ends of each set of spring arms.
SUMMARY
In accordance with one aspect of the invention, a gasket for mounting shielded electronics includes a body and a plurality of spring arms connected to the body. Each spring arm includes a free proximal portion, a free distal portion and a connection connecting the spring arm to the body. The free distal portion of each spring arm contacts a first component proximate to a first surface of the body. The free proximate portion of each spring arm contacts a second component proximate to an opposite second surface of the body. The distance between adjacent contacts on a component is less than or approximately equal to a predetermined ratio of a shielded radio wavelength.
In accordance with another aspect of the invention, a method for mounting shielded electronics to a frame is disclosed. According to the method, a gasket including a body and a plurality of spring arm portions are provided. Each spring arm includes a proximal portion, a distal portion and a connection connecting the spring arm to the body. A first component adjacent to a first surface of the body is contacted by the distal portion of each arm, and a second component adjacent to a second surface of the body is contacted by the proximal portion of each arm. The distal and proximal portions contact respective components such that the distance between adjacent contacts on a component is less than or approximately equal to a predetermined ratio of a shielded radio wavelength. Subsequently, the first component is secured to the second component.


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patent: WO99/33328 (1999-07-01), None
patent: WO 99/33328 (1999-07-01), None

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