Keyboard switch

Details Keyboard switch Keyboard switch

2000-11-28

2003-03-04

Schuberg, Darren (Department: 2835)

Electricity: electrical systems and devices

Housing or mounting assemblies with diverse electrical...

For electronic systems and devices

C200S0050EA, C400S490000

Reexamination Certificate

active

06529370

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a keyboard switch suitable for use in a notebook-type personal computer having a lid that closes to cover at least one key top. More particularly, the present invention relates to an improved keyboard switch that allows a cover-closing motion to move the key tops downward and allow the cover to easily close without undue ware.
2. Detailed Description of the Related Art
It is conventionally known to move key tops downward during a closing motion and accommodate a keyboard switch in a closed notebook-type personal computer.
Referring now to
FIGS. 12
to
14
, showing a conventional keyboard switch
100
as disclosed in the publication of Japanese Patent No. 2857353, includes a supporting plate
107
for supporting a large number of key tops
102
. Each key top
102
is attached to a cross link
101
. Keyboard switch
100
is included between a lid
115
and an equipment case
109
of a conventional notebook-type personal computer.
Cross link
101
includes a first link member
101
a
and a second link member
101
b
, each formed generally in the shape of the letter “U”, and being rotatably linked together about an intermediate rotatable fulcrum (not shown). Cross link
101
guides key top
102
during motion in an up-and-down movement.
In the operational position shown in
FIG. 13
, a dome-like rubber elastic portion
114
is disposed below each key top
102
and serves as a return spring, pressing key top
102
upward in response to a key stroke. Elastic portion
114
abuts the bottom surface of a pressure-applying portion
106
formed at the intersection between first and second link members
101
a
,
101
b.
Elastic portion
114
is integrally formed on a rubber sheet
104
superimposed on a switch sheet
103
. Switch sheet
103
, is located below elastic portion
114
, and includes an integrally formed switch portion
103
a.
Rubber sheet
104
and switch sheet
103
are both flexible and are superimposed and generally laminated together forming a flexible sheet that is slidable along a guide rail
108
included in supporting plate
107
. Switch sheet
103
and rubber sheet
104
are contactable with a return spring
118
and disposed between their end portions (not shown) and equipment case
109
. The laminated flexible sheet
103
and rubber sheet
104
are loaded by return spring
118
with a force that tends to move them toward the left-hand portion in
FIGS. 12 through 14
.
In the operational position shown in
FIGS. 12 and 13
, when downward pressure is applied to key top
102
from above, key top
102
is guided by cross link
101
and is thereby moved downward and kept generally horizontal relative to equipment case
109
without being significantly inclined. As a result, pressure-applying portion
106
of key top
102
presses on and deforms elastic portion
114
, so that an ‘ON’ operation of switch portion
103
a
is effected.
Equipment case
109
is rotatively coupled to lid
115
and rotates closed to protect key tops
102
. A cam projection
117
projects outward from the inside of lid
115
. Cam projection
117
has a top surface formed as an inclined plane. During a lid
115
closing-motion, the top surface of cam projection
117
presses on a side surface (not shown) of both switch sheet
103
and rubber sheet
104
. As the top surface of cam projection
117
presses on the side surfaces of both switch sheet
103
and rubber sheet
104
the inclined plane exerts a force that acts to counter the spring force supplied by return spring
118
. As a result of this counter-action, both switch sheet
103
and rubber sheet
104
move toward the right-hand side of
FIGS. 12 and 13
. As a result, when lid
115
is rotatably closed toward equipment case
109
, switch sheet
103
and rubber sheet
104
are slid, in a synchronization with lid
115
, into a retracted position and key tops
102
are lowered toward support plate
107
.
During closing, dome-like rubber elastic portion
114
and switch portion
103
a
retract into the lower portion of a housing concave portion
116
formed in key top
102
. Also during closing, an upward projection
104
a
, projecting from rubber sheet
104
and located near the lower leg portion of first link member
101
a
, contacts first link member
101
a
and forces cross link
101
into a retracted position as rubber sheet
104
slides leftward, as shown in FIG.
14
. Thus, simultaneous with the motion of elastic portion
114
and cross link
101
, key tops
102
move into the retracted position, reduce the overall height of keyboard switch
100
, and allow keyboard switch
100
to fit within equipment case
109
.
It should be recognized that, while key top
102
move downward into the retracted position, switch portion
103
a
remains deactivated. It should also be noted, that when key top
102
is in a retracted position, elastic portion
114
maintains an un-compressed state within concave portion
116
, thus reducing the material fatigue and increasing the operational life of elastic portion
114
.
During opening, lid
115
is rotated away key tops
102
and cam projection
117
loses contact with switch sheet
103
and rubber sheet
104
. As cam projection
117
loses contact with switch sheet
103
and rubber sheet
104
, return spring
118
forces both switch sheet
103
and rubber sheet
104
leftward into the operation position shown in FIG.
13
. In the operational position, key top
102
is supported by elastic portion
114
through cross link
101
.
It should be additionally noted that the above-described action of conventional keyboard switch
100
, shows one possible way to reduce the thickness of the equipment case
109
and hence the overall thickness of a notebook-type personal computer. It should also be noted that in conventional keyboard switch
100
, switch portion
103
a
is not activated during the closing motion and elastic portion
114
is kept in an extended state.
Additionally, in the conventional keyboard switch
100
, the inclined plane of cam projection
117
both horizontally and vertically presses on the contact surface of switch sheet
103
and rubber sheet
104
. While the horizontal-pressing motion of cam projection
117
is generally desirable in this device to activate key tops
102
, the vertical- pressing motion subjects switch sheet
103
and rubber sheet
104
to undue stress and fosters the formation of an undesirable warp along the contact surface of both sheets. Consequently, it is very difficult to achieve either a smooth sliding motion as lid
115
rotates relative to equipment case
109
or sufficient durability in switch sheet
103
and rubber sheet
104
.
Moreover, while the horizontal-pressing motion of cam projection
117
is generally desirable to activate key tops
102
, the horizontal-pressing motion also subjects switch sheet
103
and rubber sheet
104
to a compressive stress in the sliding direction. This compressive stress fosters the formation of an undesirable warp throughout flexible switch sheet
103
and rubber sheet
104
. A reinforcing lining sheet
121
, made of metal, is applied to the back surface of switch sheet
103
and rubber sheet
104
to counteract the formation of this undesirable warp. Unfortunately, lining sheet
121
increases the overall thickness of keyboard switch
100
which results in an increase in the overall thickness of a notebook-type personal compute and an increase in cost.
Furthermore, return spring
118
requires a relatively heavy spring-force to operate switch sheet
103
and rubber sheet
104
between the operational position and the retracted position and creates an increasingly complex construction.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved keyboard switch that offers durability while requiring only moderate physical force during an opening and closing operation.
It is another object of the present invention to provide an improved keyboard switch that does not require a return spring and thus re

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