Electricity: circuit makers and breakers – Solid contact – Membrane type
Reexamination Certificate
2001-03-13
2003-03-11
Luebke, Renee (Department: 2833)
Electricity: circuit makers and breakers
Solid contact
Membrane type
Reexamination Certificate
active
06531671
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a membrane circuit board switch, and more particularly, to a membrane circuit board switch with a pressure regulating reservoir.
2. Description of the Prior Art
Please refer to FIG.
1
and FIG.
2
.
FIG. 1
is a schematic diagram of a prior art membrane circuit board switch
10
used in a keyboard
12
.
FIG. 2
is a schematic diagram of a switch unit
32
of the membrane circuit board switch
10
shown in FIG.
1
. The membrane circuit board switch
10
is used in the keyboard
12
for generating key-pressing signals. The keyboard
12
comprises a base plate
14
, and a plurality of key mechanisms
16
. The membrane circuit board switch
10
is installed between the base plate
14
and the plurality of key mechanisms
16
. The membrane circuit board switch
10
comprises an upper membrane circuit
18
, a lower membrane circuit
22
, and a plurality of switch units
32
. The upper membrane circuit
18
comprises a plurality of upper contacts
20
. The lower membrane circuit
22
comprises a plurality of lower contacts
24
that correspond to the upper contacts
20
. Each upper contact
20
and its corresponding lower contact
24
form a switch unit
32
.
As shown in
FIG. 2
, the key mechanism
16
is up-and-down movably installed above the switch unit
32
for pressing the upper contact
20
to contact the lower contact
24
to generate a corresponding key-pressing signal. The lower membrane circuit
22
is positioned under the upper membrane circuit
18
. There is an interval material layered between the upper and lower membrane circuit layers for forming a predetermined space
28
with a predetermined distance
30
between the upper and lower contacts
20
,
24
. When the key mechanism
16
is depressed, the upper contact
20
is pressed down to contact the lower contact
24
. When the key mechanism
16
is released, or not depressed, the upper contact
20
will revert, or maintain the predetermined distance
30
from the corresponding lower contact
24
.
Please refer to FIG.
3
and FIG.
4
.
FIG. 3
depicts a state of the switch unit
32
shown in
FIG. 1
with lower atmospheric pressure.
FIG. 4
depicts a state of the switch unit
32
shown in
FIG. 1
with higher atmospheric pressure. Generally, there are 2 design choices of the said predetermined space
28
: interacting with the atmosphere or not. To keep unwanted particles (dust, steam etc.) out of the predetermined space
28
, the latter is usually chosen. However, when atmospheric pressure changes, the hermetic design of the predetermined space
28
can lead to malfunctioning of the switch unit
32
. As show in
FIG. 3
, when the atmospheric pressure drops (this may occur due to a change of height or temperature), the pressure inside the predetermined space
28
is higher than the atmospheric pressure. Therefore, it is not easy to make the upper contact
20
to contact the lower contact
24
. Furthermore, as shown in
FIG. 4
, when the atmospheric pressure rises, the pressure inside the predetermined space
28
becomes lower than the atmospheric pressure. Therefore, the upper contact
20
may not maintain the predetermined distance from the lower contact
24
, and thus makes unexpected contact with the lower contact
24
.
SUMMARY OF THE INVENTION
It is therefore a primary objective of the present invention to provide a membrane circuit board switch with a pressure regulating reservoir to solve the mention problems.
The present invention, briefly summarized, discloses a membrane circuit board switch used in a keyboard. The keyboard comprises a base plate, and at least one key mechanism. The membrane circuit board switch is installed between the base plate and the key mechanism. The membrane circuit board switch comprises an upper membrane circuit layer, a lower membrane circuit layer, and at least one pressure regulating reservoir communicates with the membrane circuit board switch. The upper membrane circuit layer comprises at least one upper contact. The lower membrane circuit layer comprises a corresponding lower contact. A predetermined space is formed with a predetermined distance between the upper and lower contacts by an interval material. The key mechanism can press the upper contact to contact the lower contact to generate a corresponding key-pressing signal. The pressure regulating reservoir communicates with the predetermined space to adjust the pressure inside the predetermined space. When the atmospheric pressure changes, the volume of the pressure regulating reservoir will adjust the pressure inside the predetermined space to make the predetermined distance keeping substantially constant.
It is an advantage of the present invention that the membrane circuit board switch prevents particles from entering the predetermined space, and it also adjusts the pressure inside the predetermined space to adapt to the changes of atmospheric pressure.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
REFERENCES:
patent: 4018999 (1977-04-01), Robinson et al.
patent: 4345119 (1982-08-01), Latasiewicz
patent: 4931601 (1990-06-01), Lavender
Benq Corporation
Hsu Winston
Luebke Renee
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