Electricity: conductors and insulators – Boxes and housings – Hermetic sealed envelope type
Reexamination Certificate
1999-11-08
2001-10-02
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Boxes and housings
Hermetic sealed envelope type
C174S050500, C361S752000
Reexamination Certificate
active
06297448
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an airtight case for containing electric and electronic components, which case comprises a housing and a cover and has a structure which enables an air pressure difference between the inside and outside of the case to be equalized while maintaining the air tightness of the case.
BACKGROUND ART
A circuit-carrying substrate used in a computer or in peripheral equipment thereof includes electronic components such as transistors and an electric component such as a motor. The substrate is housed in an airtight case and electrical terminals connected to the substrate circuitry extend out of the case in a connector for connection to components outside the case.
FIG.
8
(
a
) of tie accompanying drawings is a perspective view of a prior art airtight case and FIG.
8
(
b
) is a longitudinal sectional view taken on line b—b of FIG.,
8
(
a
).
This known airtight case
100
comprises a housing
70
having an opening and a cover
80
made from a metal, plastics material or the like for closing the housing opening. A plurality of electrical terminals
74
extend out of the case
100
in a connector
72
which projects outwardly from one side wall of the housing
70
. The terminals
74
of the connector
72
provide electrical connection between the circuitry of a substrate
50
fixed inside the housing
70
and components outside the case
70
.
After the substrate
50
has been mounted inside the housing
70
, a sealing packing
90
is interposed between the rim of the opening of the housing
70
and the cover
80
, and the housing
70
and the cover
80
are secured together by fasteners, such as screws
60
.
The resulting airtight case
100
must be completely waterproof to prevent water from entering the inside of the case.
Thus, if the inside of the airtight case
100
communicates with the outside air, the conditions of the outside air, such as the temperature and moisture of the outside air, may affect the substrate
50
inside the case
100
. In particular, if humid outside air enters the inside of the airtight case
100
, metal portions such as the circuitry of the substrate
50
may be corroded by the water contained in the outside air and thereby cause an electrical contact failure.
The airtight case
100
must therefore have excellent air-tightness.
When an electric or electronic part inside the airtight case
100
generates heat and the temperature inside the airtight case
100
rises, the pressure in the case
100
increases due to the expansion of the air within the case. Similarly, depending on the conditions, the pressure inside the airtight case
100
may become lower than atmospheric pressure.
To equalize such pressure differences between the inside and outside of the airtight case
100
, through holes may be formed in the airtight case
100
.
However, if through holes are formed in the case
100
, the above waterproofness and air-tightness are inevitably impaired.
To cope with this, it has been proposed to use an airtight case of the form shown in
FIG. 9
of the drawings. In the airtight case
102
shown in
FIG. 9
, a through hole
704
opening into the connector
72
is formed in the side wall of housing
702
of the case
102
and a sealing packing
902
is provided between the connector
72
and the connector
72
′ of a component D to which the connector
72
is connected to prevent the through hole
704
from being exposed to the outside air. In another known arrangement shown in
FIG. 10
, a through hole
714
formed in the side surface of a housing
712
of an airtight case
104
is covered with cloth
716
serving to transmit only air and not moisture. These prior art structures attempt in this way to eliminate any pressure difference between the inside and outside of the airtight case
102
or
104
whilst maintaining the waterproofness and air-tightness of the case.
However, as will be clear from
FIG. 9
, even with the case
102
having the through hole
704
opening into the connector
72
and the packing
902
around the connector, it is impossible to retain air-tightness completely and thus impossible to prevent outside air containing moisture from entering the inside of the airtight case
102
.
Further, as shown in
FIG. 10
, if the rough hole
714
of the airtight case
104
, covered with the cloth
716
for transmitting only air and not water, becomes blocked with water, it no longer functions as a pressure control hole.
As described above, it is therefore difficult using the airtight cases
100
,
102
and
104
of the prior art to eliminate a pressure difference between the inside and outside of the case while retaining the air-tightness of the case.
When it is also necessary to use the sealing packing
90
or
902
, there is a further problem in that the number of parts and the production cost is increased.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided an inner and outer structure for an airtight case containing electric and electronic components and including a housing having an opening closed by a cover, in which structure a diaphragm portion made from a flexible material is integrated with the cover or the housing.
Therefore, when a pressure difference is generated between the inside and the outside of the airtight case, the diaphragm portion made from a flexible material and integrated with the cover or the housing is elastically deformed by the pressure difference, changes the inner volume of the airtight case and thereby alleviates the pressure difference between the outside and the inside of the airtight case without there being any communication between the inside of the case and the outside air.
According to a second aspect of the present invention, there is provided an inner and outer pressure equalizing structure for an airtight case containing electric and electronic components and including a housing having an opening closed by a cover, in which structure: a diaphragm having a projecting portion is sandwiched between the housing and the cover; the cover has a cut-out, and the projecting portion of the diaphragm is received in the cut-out.
Also in this case, when a pressure difference is generated between the inside and outside of the airtight case, the diaphragm having the projecting portion is elastically deformed by the pressure difference, changes the inner capacity of the airtight case and thereby alleviates the pressure difference between the inside and the outside of the airtight case without communicating with the outside air.
REFERENCES:
patent: 2462445 (1949-02-01), Weiss
patent: 3607604 (1971-09-01), Nava
patent: 4145588 (1979-03-01), Orcutt
patent: 5081327 (1992-01-01), Graham et al.
patent: 5434748 (1995-07-01), Fukui et al.
patent: 5497290 (1996-03-01), Fukui et al.
patent: 58-69991 (1993-05-01), None
patent: 51-60579 (1993-06-01), None
Duane Morris & Heckscher LLP
Estrada Angel R.
Reichard Dean A.
Tokai Kogyo Co. Ltd.
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