Integrated switch bank

Details Integrated switch bank Integrated switch bank

2003-05-08

2004-05-18

Friedhofer, Michael A. (Department: 2832)

Electricity: circuit makers and breakers

Electric switch details

Indicators

C200S314000, C200S317000, C200S517000, C200S341000

Reexamination Certificate

active

06737596

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system and a method for an integrated switch bank.
2. Background Art
Referring to
FIG. 1
a
, a diagram
10
illustrating a conventional switch bank (or array) is shown. The switch bank
10
is a stacked (i.e., overlaid) structure. The switch back
10
is implemented to carry a low voltage DC signal. The switch bank
10
is a group of normally open, single pole, single throw (NO, SP, ST) momentary contact device non-tactile switches. The switch bank
10
includes a graphic overlay
12
having painted or printed on symbols
14
a
-
14
n
that relate to numbers, arithmetic operators, and the like depending on the switch bank
10
application. In one example, the overlay
12
is disposed over an electrostatic discharge (ESD)/electromagnetic interference (EMI) shield
16
. In another example, the overlay
12
is disposed directly over a top membrane
18
. The membrane
18
has a number of contacts
20
a
-
20
n
that align with the respective symbols
14
a
-
14
n
when the switch bank
10
is properly assembled.
The switch bank
10
further includes a spacer
22
disposed under the membrane
18
. The spacer
22
has holes
24
a
-
24
n
that generally align with respective contacts
20
a
-
20
n
in membrane
18
. A bottom membrane (or circuit board)
30
includes circuit grids
32
a
-
32
n
that generally align with respective contacts
20
a
-
20
n
such that a respective circuit is closed when a user sufficiently depresses the respective symbol
14
. The switch bank
10
can also include a subpanel (i.e., substrate, back cover, etc.)
34
that generally provides physical support. The stackup or overlay of the respective symbol
14
, contact
20
, hole
24
, and grid
32
forms an individual switch in the switch bank
10
.
The conventional switch bank
10
has a number of deficiencies that include when the switch bank
10
is manufactured, the layers (i.e., the overlay
12
, the membrane
18
, the spacer
22
, the circuit board
30
, and the subpanel
34
) can be difficult to align such that the respective symbols, holes, and circuits align properly, the switch bank
10
is not lighted or backlit, the overlay
12
and the symbols
14
are not registered (i.e., the surface of the overlay
12
is substantially smooth such that a user can not readily discern switch location and type by feel), and the switch bank
10
does not provide tactile feedback feel to the user.
However, the user generally prefers switches that have a tactile feel such that actuation of the switch provides positive feedback such as a snap to indicate switch operation. A tactile switch can be defined (e.g., by American Society for Testing and Materials standards ASTM F 1570-01e1 and F 1997-99) as a switch having a tactile ratio greater than zero. Furthermore, tactile indication of the respective switch symbol and/or switch lighting is desirable in many applications such that the user can readily identify the appropriate switch in a low light environment.
Referring to
FIG. 1
b
, a diagram illustrating a conventional switch bank
10
′ is shown. The conventional switch bank
10
′ is similar to the switch bank
10
. To provide a tactile feel, the switch bank
10
′ includes a spacer
40
disposed between the overlay
12
and a membrane
18
′. The membrane
18
′ implements domes
20
a
′-
20
n
′ instead of the membrane contacts
20
a
-
20
n
of switch bank
10
. Depressing the membrane
12
at a symbol
14
of the switch bank
10
′ collapses a respective dome
20
′ to provide the tactile response to the user. However, the conventional switch bank
10
′ has a number of deficiencies. During manufacturing the layers can be difficult to align such that the respective symbols, domes, holes, and circuits align properly. The switch bank
10
′ is not lighted, and the overlay
12
and the symbols
14
do not provide tactile registration.
Referring to
FIG. 1
c
, a diagram illustrating a conventional switch bank
10
″ is shown. The switch bank
10
″ is implemented similarly to the switch banks
10
and
10
′. To provide a tactile feel switch bank, the switch bank
10
″ has a non-tactile overlay
12
″ made of an elastomer rubber having raised symbols
14
″ (i.e., buttons) to provide the tactile registration. The membrane
18
′ can provide a limited tactile feel. The switch bank
10
″ also substitutes an adhesive spacer
22
″ for the spacer
22
. However, during manufacturing the layers can be difficult to align such that the respective symbols, domes, holes, and circuits align properly. The switch bank
10
″ is not lighted, and the tactile feel provided by the membrane
18
′ is reduced by the relatively thick and soft buttons
14
″.
Referring to
FIG. 2
a
, a diagram illustrating an exploded, sectional view of a conventional switch (or cell)
50
is shown. A number of the switches
50
may be integrated (i.e., combined or implemented as an array) to provide a switch bank similar to the switch banks
10
,
10
′, and
10
″. The switch
50
includes an overlay/bezel
52
with a hole that has a shape similar to a key top (or cap)
54
. The key top
54
is hard plastic and protrudes through the bezel
52
and the bezel
52
generally positions the key top
54
. The key top
54
is disposed onto a rubber keypad
56
that has a carbon or metallic pill (or puck)
58
on top of a dome
60
. The dome
60
is disposed above a bottom membrane (or circuit board)
62
that has a circuit grid
64
. The switch
50
may be disposed on a subpanel (i.e., substrate, back cover, etc.)
66
that provides physical support. To actuate the switch
50
, the user depresses the key top
54
, the key top
54
collapses the dome
60
, and the pill
58
contacts the grid
64
to complete a circuit. The dome
60
provides tactile feel to the switch
50
, however, the tactile feel is limited by the interface between the cap
54
and the pill
58
.
The conventional switch bank
50
is not sealed at the interface between the bezel
52
and the key top
54
and debris can enter the interface and interfere with proper switch operation. During manufacturing the layers (i.e., the bezel
52
, the key top
54
, the keypad
56
, and the membrane
62
) can be difficult to align (i.e., gaps can be difficult to control) such that the respective key tops, domes, and circuits align properly, and the switch
50
is not lighted. Each key top
54
is typically individually molded, painted and assembled into the switch
50
assembly.
The alignment of the bezel
52
and the key top
54
is critical to the proper operation and feel of the switch
50
. When the gaps between the bezel
52
and the key top
54
are not properly sized or aligned the key tops
54
can be too tight and bind, too loose and wobble and result in reduction or loss of tactile feel, and in any case fail to cause the pill
58
to properly contact the grid
64
.
Referring to
FIG. 2
b
, a diagram illustrating a conventional switch (or cell)
50
′ is shown. The switch
50
′ is implemented similarly to the switch
50
. The switch
50
′ includes a tactile rubber keypad
56
′ having a formed key
54
′ that protrudes through the bezel
52
. The key
54
′/keypad
56
′ can be formed from a dual durometer molding where the key
54
′ is implemented using a rubber that is harder than the keypad
56
′. The pill
58
is fixed to the underside of the key
54
′. The conventional switch bank
50
′ has similar deficiencies to the switch
50
.
Referring to
FIG. 2
c
, a diagram illustrating a conventional switch (or cell)
50
″ is shown. The switch
50
″ is implemented similarly to the switches
50
and
50
′. The switch
50
″ includes a non-tactile rubber keypad
56
″ having a formed key
54
″ that protrudes through the bezel
52
. The pill
58
is fixed to the underside of the key
54
″.

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