Pointing stick with increased sensitivity

Details Pointing stick with increased sensitivity Pointing stick with increased sensitivity

2001-04-25

2002-06-25

Enad, Elvin (Department: 2832)

Electrical resistors

Resistance value responsive to a condition

Force-actuated

C338S002000, C338S114000, C200S00600C, C200S00600C

Reexamination Certificate

active

06411193

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a pointing stick, and more particularly, to a pointing stick with increased sensitivity.
2. Description of the Prior Art
A pointing stick, used for controlling the movements and position of a cursor on a computer display, is used in many types of devices, such as keyboards, mice, joysticks, and remote controls.
Please refer to FIG.
1
and FIG.
2
.
FIG. 1
is a perspective view of a prior art pointing stick
10
, and
FIG. 2
is an operational diagram of the pointing stick
10
. The pointing stick
10
includes a base
12
, a rod
18
, a cruciform foundation plate
20
, and four strain gauges
16
set on a bottom side
22
of the cruciform foundation plate
20
. The rod
18
is set perpendicular to the middle portion of the cruciform foundation plate
20
. As shown in FIG.
FIG. 2
, the cruciform foundation plate
20
bends while be pressed from the top end of the rod
18
and, as a result, the strain gauges
16
stuck to the bottom side
22
of the cruciform foundation plate
22
deform to generate corresponding sensing signals.
As shown in
FIG. 2
, each strain gauge
16
includes a pressure resistor
24
, a first electrode
26
, and a second electrode
28
. The pressure resistor
24
deforms according to the bending of the cruciform foundation plate
20
, and thus offers a varying resistance. The first electrode
26
and the second electrode
28
are set on the right and the left side of the pressure resistor
24
respectively for allowing a current L to flow from the first electrode
26
, through the pressure resistor
24
, and to the second electrode
28
. While the pressure resistor
24
is deformed horizontally, the horizontal resistance of the pressure resistor
24
varies also, leading to variation of the current L to generate corresponding sensing signals.
But the pointing stick
10
relies only on the bending of the cruciform foundation plate
20
for deforming the pressure resistor
24
to output sensing signals. Therefore, the sensitivity of the strain gauge
16
relies solely on the elasticity of the cruciform foundation plate
20
, and so is not as sensitive as possible.
SUMMARY OF THE INVENTION
It is therefore the objective of the present invention to provide a pointing stick with increased sensitivity.
In accordance with the claimed invention, a pointing stick includes a substrate, an input pillar set perpendicular to the substrate, and at least one strain gauge for sensing pressure and producing pointing signals corresponding to the pressure. A portion of the strain gauge is set between the input pillar and the substrate. The strain gauge includes a first pressure resistor set on an upper surface of the substrate. A first electrode and a second electrode are electrically connected to the first pressure resistor. The first electrode and the second electrode form a loop to pass current through the first pressure resistor. The first electrode and the second electrode are separated by a gap with a predetermined distance in a pressing direction, which is perpendicular to the surface of the substrate.
It is an advantage of the present invention that the gap between the first electrode and the second electrode increases the sensitivity in the pressing direction so that the pointing stick of the present invention produces pointing signals not only according to the bend of the pointing stick itself but also according to deformation in the pressing direction.
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: 5325081 (1994-06-01), Roberts
patent: 5543592 (1996-08-01), Gaultier et al.
patent: 5659334 (1997-08-01), Yaniger et al.
patent: 5867808 (1999-02-01), Belker et al.
patent: 6107993 (2000-08-01), DeVolpi
patent: 6137475 (2000-10-01), Ginn et al.
patent: WO 00/30027 (2000-05-01), None

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