U.S. patent number RE41,521 [Application Number 11/703,845] was granted by the patent office on 2010-08-17 for variable capacity condenser and pointer.
This patent grant is currently assigned to Wacom Co., Ltd.. Invention is credited to Hiroyuki Fujitsuka, Yasuyuki Fukushima.
United States Patent |
RE41,521 |
Fukushima , et al. |
August 17, 2010 |
Variable capacity condenser and pointer
Abstract
The present invention provides a variable capacity condenser
having fewer components. A variable capacity condenser according to
the present invention comprises a dielectric substance, two
electrodes, and a flexible electrode. The dielectric substance has
two end faces. The two electrodes are disposed on one end face of
the dielectric substance. The flexible electrode faces the other
end face of the dielectric substance. The flexible electrode is
pressible by a pressing member to vary a distance between at least
a portion of the flexible electrode and the other end face of the
dielectric substance.
Inventors: |
Fukushima; Yasuyuki
(Saitama-ken, JP), Fujitsuka; Hiroyuki (Saitama-ken,
JP) |
Assignee: |
Wacom Co., Ltd. (Saitama-Ken,
JP)
|
Family
ID: |
18642484 |
Appl.
No.: |
11/703,845 |
Filed: |
February 8, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
Reissue of: |
09837368 |
Apr 19, 2001 |
06853369 |
Feb 8, 2005 |
|
|
Foreign Application Priority Data
|
|
|
|
|
May 8, 2000 [JP] |
|
|
2000-134154 |
|
Current U.S.
Class: |
345/179;
361/283.1; 178/19.04; 361/283.2; 178/19.01 |
Current CPC
Class: |
H01G
5/014 (20130101); G06F 3/03545 (20130101); H01G
5/0136 (20130101); H01G 5/16 (20130101) |
Current International
Class: |
G09G
5/00 (20060101) |
Field of
Search: |
;345/156-184
;178/18.01,19.01,19.04 ;73/862.69,718 ;361/283.1,283.2,280,287,291
;33/366 ;340/689 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
60-153629 |
|
Aug 1985 |
|
JP |
|
4-96212 |
|
Mar 1992 |
|
JP |
|
04-096212 |
|
Mar 1992 |
|
JP |
|
05-275283 |
|
Oct 1993 |
|
JP |
|
5-275283 |
|
Oct 1993 |
|
JP |
|
Primary Examiner: Kumar; Srilakshmi K
Attorney, Agent or Firm: Berenato & White, LLC
Claims
What is claimed is:
1. A variable capacity condenser comprising: a dielectric substance
of an electric pointer device having two end faces; two electrodes
disposed on one end face of the dielectric substance; and a
flexible electrode facing the other end face of the dielectric
substance and pressible by a pressing member to vary a distance
between at least a portion of the flexible electrode and the other
end face of the dielectric substance.
2. The variable capacity condenser according to claim 1, wherein
the flexible electrode comprises a mixture of rubber and conductive
particles.
3. The variable capacity condenser according to claim 2, wherein
the conductive particles are carbon particles.
4. The variable capacity condenser according to claim 1, wherein
the flexible electrode is a deposition film.
5. The variable capacity condenser according to claim 1, further
comprising an elastic member positioned between the flexible
electrode and the pressing member.
6. The variable capacity condenser according to claim 1, further
comprising a spacer positioned between the other end face of the
dielectric substance and the flexible electrode.
7. A pointer comprising: a casing; a circuit disposed within the
casing, the circuit including a variable capacity condenser
comprising: a dielectric substance having two end faces; two
electrodes disposed on one end face of the dielectric substance;
and a flexible electrode facing the other end face of the
dielectric substance; and a pressing member to press the flexible
electrode of the variable capacity condenser to vary a distance
between at least a portion of the flexible electrode and the other
end face of the dielectric substance.
8. The pointer according to claim 7, wherein the flexible electrode
of the variable capacity condenser comprises a mixture of rubber
and conductive particles.
9. The pointer according to claim 8, wherein the conductive
particles are carbon particles.
10. The pointer according to claim 7, wherein the flexible
electrode of the variable capacity condenser is a deposition
film.
11. The pointer according to claim 7, wherein the variable capacity
condenser further comprises an elastic member positioned between
the flexible electrode and the pressing member.
12. The pointer according to claim 7, wherein the variable capacity
condenser further comprises a spacer positioned between the other
end face of the dielectric substance and the flexible
electrode.
13. The pointer according to claim 7, wherein the casing is
pen-shaped and the pointer includes a core having a pen point
protruding outside the casing to transmit pressure applied thereto
to the variable capacity condenser.
14. The pointer according to claim 13, wherein the pressing member
is a ferrite core made integral with the core and having a coil
wound therearound.
15. The pointer according to claim 13, wherein the pressing member
is the core slidable through a ferrite core having a coil wound
therearound.
16. The pointer according to claim 7, further comprising a circuit
substrate having front and back sides, each of the front and back
sides including at least a portion of the circuit printed thereon,
the at least a portion of the circuit printed on the front side
including a conducting portion electrically connected to one of the
two electrodes and the at least a portion of the circuit printed on
the back side including a conducting portion electrically connected
to the other of the two electrodes.
17. The pointer according to claim 16, the conducting portions are
soldered to the two electrodes.
18. The pointer according to claim 16, wherein the conducting
portions are provided around an end face of the circuit substrate
abutting the one end face of the dielectric substance at a portion
separating the two electrodes by a predetermined distance.
19. The pointer according to claim 18, wherein the circuit
substrate has a thickness substantially equal to the predetermined
distance of the portion of the dielectric substance separating the
two electrodes.
.Iadd.20. A variable capacity condenser comprising: a dielectric
region of an electric pointer including a dielectric substance, the
dielectric region having two end portions; two electrodes disposed
at one end portion of the dielectric region; and a flexible
electrode facing the other end portion of the dielectric region and
pressible by a pressing member to vary a distance between at least
a portion of the flexible electrode and the other end portion of
the dielectric region..Iaddend.
.Iadd.21. The variable capacity condenser according to claim 20,
further comprising a spacer positioned between the other end
portion of the dielectric region and the flexible
electrode..Iaddend.
.Iadd.22. The variable capacity condenser according to claim 20,
wherein the dielectric substance has a disc shape that defines the
shape of the dielectric region..Iaddend.
.Iadd.23. A variable capacity condenser, comprising: a dielectric
region of an electric pointer defined by at least one dielectric
substance disposed therein, the dielectric region having a
substantially cylindrical shape with a circumferential side portion
and circular end faces disposed on opposite sides of the
circumferential side portion; two electrodes disposed at a first
one of the circular end faces of the dielectric region; and a
flexible electrode facing a second one of the circular end faces of
the dielectric region and pressible by a pressing member to vary a
distance between at least a portion of the flexible electrode and
the second circular end face of the dielectric region..Iaddend.
.Iadd.24. The variable capacity condenser according to claim 23,
wherein the two electrodes are disposed on the at least one
dielectric substance..Iaddend.
.Iadd.25. The variable capacity condenser according to claim 23,
wherein the two electrodes are disposed at two semicircular halves
of the first circular end face of the dielectric
region..Iaddend.
.Iadd.26. A variable capacity condenser usable in an electric
pointing device, the condenser comprising: a dielectric region of
an electric pointer, the dielectric region having a disc shape
defined by a dielectric substance disposed therein, the disc-shaped
dielectric region having upper and lower end portions and a side
portion connected between the upper and lower end portions; two
electrodes disposed at the upper end portion of the dielectric
region; and a flexible conductive member facing the lower end
portion of the dielectric region; and pressible by a pressing
member to vary a distance between at least a portion of the
flexible electrode and the lower end portion of the dielectric
region..Iaddend.
.Iadd.27. The variable capacity condenser according to claim 26,
wherein the dielectric substance has a disc shape..Iaddend.
.Iadd.28. A variable capacity condenser comprising: a dielectric
region of an electric pointer having two end portions, the
dielectric region including at least two different dielectrics; two
electrodes disposed at one end portion of the dielectric region;
and a flexible conductive member facing the other end portion of
the dielectric region; and pressible by a pressing member to vary a
distance between at least a portion of the flexible electrode and
an the other end portion of the dielectric region..Iaddend.
.Iadd.29. The variable capacity condenser according to claim 28,
wherein the dielectric region has a disc shape with the two end
portions disposed on opposite sides of a circumferential side
portion..Iaddend.
.Iadd.30. A variable capacity condenser comprising: a dielectric
component of an electric pointer device having two end faces; two
electrodes disposed on one end face of the dielectric component;
and a flexible electrode facing the other end face of the
dielectric component and pressible by a pressing member to vary a
distance between at least a portion of the flexible electrode and
the other end face of the dielectric component..Iaddend.
.Iadd.31. The variable capacity condenser according to claim 30,
wherein the dielectric component comprises at least two different
dielectrics..Iaddend.
.Iadd.32. A variable capacity condenser comprising: a generally
circular dielectric component of an electric pointer device having
upper and lower end portions; a ring shaped spacer disposed beneath
the lower end portion of the dielectric component; first and second
electrodes disposed on the upper end portion of the dielectric
component; and a circular flexible electrode disposed beneath the
ring shaped spacer to face the lower end portion of the dielectric
component, the flexible electrode being pressible to vary a
distance between at least a portion of the flexible electrode and
the first and second electrodes..Iaddend.
.Iadd.33. A variable capacity condenser usable with an electric
pointer, the condenser comprising: a first capacity condenser
having a first dielectric portion, a first upper electrode disposed
on the first dielectric portion, and a first lower electrode
portion disposed beneath the first dielectric portion; and a second
capacity condenser disposed adjacent to the first capacity
condenser and having a second dielectric portion, a second upper
electrode disposed on the second dielectric portion, and a second
lower electrode portion disposed beneath the second dielectric
portion, wherein the first and second lower electrode portions are
movable with respect to the first and second upper electrode
portions, respectively, to change capacities
therebetween..Iaddend.
.Iadd.34. The variable capacity condenser according to claim 33,
wherein the first and second dielectric portions comprises a
generally circular dielectric component..Iaddend.
.Iadd.35. The variable capacity condenser according to claim 33,
wherein the first and second dielectric portions comprise a
dielectric disc..Iaddend.
.Iadd.36. The variable capacity condenser according to claim 33,
wherein the first and second dielectric portions comprise
semicircular dielectric components..Iaddend.
.Iadd.37. The variable capacity condenser according to claim 36,
wherein the first and second upper electrodes comprise semicircular
flat electrodes disposed on the corresponding semicircular
dielectric components..Iaddend.
.Iadd.38. A variable capacity condenser comprising: an integrated
capacitor of an electric pointer, the integrated capacitor
including at least two individual electrodes, a movable common
electrode movable with respect to the individual electrodes, and
dielectric disposed between the individual electrodes and the
movable common electrode, the movable common electrode being
movable by operation of the electric pointer such that a distance
between the movable common electrode and the individual electrodes
is varied..Iaddend.
.Iadd.39. The variable capacity condenser according to claim 38,
wherein the movable common electrode comprises a flexible
conductive member spaced apart from the dielectric, and the
individual electrodes are disposed on the dielectric and have
shapes that correspond to different halves of the flexible
electrode..Iaddend.
.Iadd.40. The variable capacity condenser according to claim 38,
wherein the dielectric includes at least two different
dielectrics..Iaddend.
.Iadd.41. A variable capacity condenser comprising: a generally
circular dielectric component of an electric pointer device having
two end faces; two electrodes disposed on one end face of the
dielectric component; and a flexible electrode facing the other end
face of the dielectric component and pressible by a pressing member
to vary a distance between at least a portion of the flexible
electrode and the other end face of the dielectric
component..Iaddend.
.Iadd.42. A variable capacity condenser comprising: a dielectric
region of an electric pointer, the dielectric region having two end
portions; a dielectric substance; two electrodes at one of the end
portions of the dielectric region, and a conductive elastic
material at the other end portion, wherein, the conductive elastic
material at one end portion is flexible by a control with which a
distance is altered between at least one electrode at one end
portion and the conductive elastic material at the other end
portion of the dielectric region, and wherein, the capacity of the
variable capacity condenser changes in relation to changes in said
distance..Iaddend.
.Iadd.43. The variable capacity condenser according claim 42,
further comprising a spacer positioned between the other end
portion of the dielectric region and the conductive elastic
material..Iaddend.
.Iadd.44. The variable capacity condenser according to claim 42,
wherein the dielectric substance has a disc shape that defines the
shape of the dielectric region..Iaddend.
.Iadd.45. A variable capacity condenser, comprising: a dielectric
region of an electric pointer defined by at least one dielectric
substance disposed therein, the dielectric region having a
substantially cylindrical shape with a circumferential side portion
and circular end faces disposed on opposite sides of the
circumferential side portion; two electrodes disposed at a first
one of the circular end faces of the dielectric region; and a third
electrode facing a second one of the circular end faces of the
dielectric region, wherein, the third electrode is movable by a
control with which a distance is altered between the third
electrode and the second one of the circular end faces of the
dielectric region, and wherein, the capacity of the variable
capacity condenser changes in relation to alterations in said
distance..Iaddend.
.Iadd.46. The variable capacity condenser according to claim 45,
wherein the two electrodes are disposed on the at least one
dielectric substance..Iaddend.
.Iadd.47. The variable capacity condenser according to claim 45,
wherein the two electrodes are disposed at two semicircular halves
of the first circular end face of the dielectric
region..Iaddend.
.Iadd.48. The variable capacity condenser according to claim 45,
wherein the third electrode is flexible..Iaddend.
.Iadd.49. A variable capacity condenser usable in an electric
pointing device, the condenser comprising: a dielectric region of
an electric pointer, the dielectric region having a disc shape
defined by a dielectric substance disposed therein, the disc-shaped
dielectric region having upper and lower end portions and a side
portion connected between the upper and lower end portions; two
electrodes disposed at the upper end portion of the dielectric
region; and a third electrode facing the lower end portion of the
dielectric region, wherein, the third electrode is movable by a
control with which a distance is altered between the third
electrode and the second one of the circular end faces of the
dielectric region, and wherein, the capacity of the variable
capacity condenser changes in relation to changes in said
distance..Iaddend.
.Iadd.50. The variable capacity condenser according to claim 49,
wherein the dielectric substance has a disc shape..Iaddend.
.Iadd.51. The variable capacity condenser according to claim 49,
wherein the third electrode is flexible..Iaddend.
.Iadd.52. A variable capacity condenser comprising: a dielectric
component of an electric pointer device having two end faces; two
electrodes disposed on one end face of the dielectric component;
and a movable electrode facing the other end face of the dielectric
component, wherein, the movable electrode is actuated by a control
to vary a distance between at least a portion of the movable
electrode and the other end face of the dielectric component, and
wherein, the capacity of the variable capacity condenser changes in
relation to changes in said distance..Iaddend.
.Iadd.53. The variable capacity condenser according to claim 52,
wherein the dielectric component comprises at least two different
dielectrics..Iaddend.
.Iadd.54. The variable capacity condenser according to claim 52,
wherein the movable electrode is flexible..Iaddend.
.Iadd.55. A variable capacity condenser comprising: a generally
circular dielectric component of an electric pointer device having
upper and lower end portions; a ring shaped spacer disposed beneath
the lower end portion of the dielectric component; first and second
electrodes disposed on the upper end portion of the dielectric
component; and a circular movable electrode disposed beneath the
ring shaped spacer to face the lower end portion of the dielectric
component, the movable electrode being pressible to vary a distance
between at least a portion of the movable electrode and the first
and second electrodes..Iaddend.
.Iadd.56. The variable capacity condenser according to claim 55,
wherein the movable electrode is flexible..Iaddend.
Description
.Iadd.Claim to priority. This application claims priority to patent
application Ser. No. 2000-134154, filed May 8, 2000 in
Japan..Iaddend.
BACKGROUND OF THE INVENTION
The present invention relates to a variable capacity condenser.
More particularly, the present invention relates to a variable
capacity condenser to be used in a pointer for inputting a
coordinate into a computer.
Prior art variable capacity condensers to be used in a pointer are
disclosed in Japanese laid-open patent publication Nos. 4-96212 and
5-275283. FIG. 8 illustrates a pointer in the form of an electric
pen (hereinafter referred to as a hard-type electric pen) disclosed
in Japanese laid-open patent publication No. 4-96212. The electric
pen illustrated in FIG. 8 comprises an electric pen casing 801 and
a circuit substrate 814. A resonance circuit is provided on the
circuit substrate 814 and cooperates with a pointing device to
input a coordinate of the electric pen into a computer (not shown).
Although not illustrated in FIG. 8, a pointing device,
conventionally referred to as a tablet, typically includes a flat
input surface having many loop coils arranged in parallel and in
every direction. The tablet detects and inputs into a computer a
coordinate position as well as a tool force of the electric pen by
an electromagnetic exchange between the resonance circuit of the
electric pen and a loop coil in the tablet.
The resonance circuit provided on the circuit substrate 814
includes a fixed condenser 813, a variable capacity condenser, and
a coil 803. The variable capacity condenser mainly includes a
dielectric substance 808, an electrode 809, and a deposition film
816. The electrode 809 is provided on one end face of the
dielectric substance 808 by baking. A pin 811 electrically connects
the electrode 809 to a terminal in the resonance circuit. The
deposit film 816, a second electrode, faces the other end face of
the dielectric substance 808. A pin 812 electrically connects the
deposit film 816 to another terminal in the resonance circuit.
The variable capacity condenser further includes a spacer 807 and a
silicon rubber 815. The spacer 807 is positioned between the other
end face of the dielectric substance 808 and the deposit film 816.
The silicon rubber 815 is positioned between the deposit film 816
and a core holder 804. As illustrated in FIG. 8, an upper switching
case 810 and a lower switching case 805 clip the components of the
variable capacity condenser (dielectric substance 808, the
electrode 809, the pin 811, the spacer 807, the deposit film 816,
the pin 812, and the silicon rubber 815) as well as the core holder
804.
As illustrated in FIG. 8, a core 802 has a pen point protruding
outside the electric pen casing 801. As pressure is applied to the
pen point, the core 802 slides through a ferrite core 823 having
coils 803 would therearound. The core holder 804 provided at the
back end of the core 802 then presses the deposit film 816 via the
silicon rubber 815 and decreases the distance between a portion of
the deposit film 816 and the other end of the dielectric substance
808. A portion of the deposit film 816 contacts the other end face
of the dielectric substance 808 and the contact area increases as
the pressure applied to the pen point increases. As the contact
area increases, the air disposed between the deposit film 816 and
the other end face of the dielectric substance 808 is expelled.
Consequently, the capacity of the variable capacity condenser
changes as less air contributes as a dielectric material.
As a result, a resonance frequency of the resonance circuit is
deviated because the combined capacity of the variable capacity
condenser and the fixed condenser 813 changes. A pointing device
(e.g., a tablet) detects this deviant resonance frequency, which
depends on the amount of pressure applied to the pent point of the
core 802. FIG. 11 illustrates a tool force detected by a pointing
device versus a load applied to the pen point of the hard-type
electric pen shown in FIG. 8.
In the hard-type electric pen shown in FIG. 8, the ferrite core 823
is a cylindrical core made of L6 member. The ferrite core 823 has
an outer diameter of 4 mm, an inner diameter of 2 mm, and a length
of 17.5 mm. The coil 803 is a wire of ULAP7/0.07 wound around the
ferrite core 823 thirty seven turns. The coil 803 contacts the
surface of the ferrite core 823 and is wound around without any
gaps between the turns. The coil 803 has an inductance L=26 .mu.H,
Q=145 (a frequency of 500 kHz). The dielectric substance 808 is a
ceramic with a titanic acid barium system and has an outer diameter
of 4 mm and a thickness of 1 mm. Please note that the outer
diameter of the dielectric substance 808 and that of the ferrite
cover 823 are the same. FIG. 8, showing the outer diameter of the
dielectric substance 808 being greater than that of the ferrite
core 823, is not drawn to scale. The electrode 809 is deposited on
the one end face of the dielectric substance 808. The other end
face of the dielectric substance 808 is mirror-finished. The
silicon rubber 815 has a thickness of 0.4 mm and an outer diameter
of 4 mm. As the spacer 807, UPILEX.TM. of 40 micrometers is used.
The spacer 807 is toroidal in shape and has an outer diameter of 4
mm and an inner diameter of 3.3 mm. As the deposit film 816,
UPILEX.TM. of 75 micrometers is used. Nickel chrome having a
thickness of 1000 angstroms is deposited on the deposit film
816.
FIG. 7 illustrates a pointer in the form of an electric pen
(hereinafter referred to as a soft-type electric pen) disclosed in
Japanese laid-open patent publication No. 5-275283. The electric
pen shown in FIG. 7 differs from the hard-type electric pen shown
in FIG. 8 in its various capacity condenser. By having a modified
variable capacity condenser, the electric pen shown in FIG. 7
reacts to a lighter load.
In the soft-type electric pen, a conductive rubber 706, comprising
a mixture of synthetic rubber and conductive particles, replaces
the deposit film 816 and the silicon rubber 815 of the hard-type
electric pen. In addition, the thickness and inner diameter of a
spacer 707 change from those of the spacer 807. Furthermore,
instead of a mirror-finished surface of the dielectric substance
808, the other end face of a dielectric substance 708 is a harsh
surface ground by a file No. 320. These modifications produce a
tool force-load property illustrated in FIG. 10.
A comparison of FIGS. 10 and 11 reveals that the soft-type electric
pen reacts to a lighter touch than the hard-type electric pen. For
example, FIG. 10 shows that the soft-type electric pen generates a
tool force of about 55 when a load of 50 g is applied. For the same
applied load of 50 g, however, FIG. 11 shows that the hard-type
electric pen generates a tool force of about 30.
In the soft-type electric pen, a ferrite cover 723 is a cylindrical
core made of L6 member. The ferrite core 723 has an outer diameter
of 4 mm, an inner diameter of 2 mm, and a length of 17.5 mm. The
coil 703 is a wire of ULAP7/0.07 wound around the ferrite core 723
thirty seven turns. The coil 703 contacts the surface of the
ferrite core 723 and is wound around without any gaps between the
turns. The coil 703 has an inductance L=26 .mu.H, Q=145 (a
frequency of 500 kHz). A dielectric substance 708 is a ceramic with
a titanic acid barium system and has an outer diameter of 4 mm and
a thickness of 1 mm. Please note that the outer diameter of the
dielectric substance 708 and that of the ferrite core 723 are the
same. FIG. 7, showing the outer diameter of the dielectric
substance 708 being greater than that of the ferrite core 723, is
not drawn to scale. An electrode 709 is burned into one end face of
the dielectric substance 708. The other end face of the dielectric
substance 708 is ground by a file No. 320. As the spacer 707,
UPILEX.TM. of 75 micrometers is used. The spacer 707 is toroidal in
shape and has an outer diameter of 4 mm and an inner diameter of
2.4 mm. The conductive rubber 706 has a thickness of 0.4 mm and an
outer diameter of 4 mm.
The conductive rubber 706 comprises a mixture of synthetic rubber
and carbon particles. The conductive rubber 706 functions as an
electrode because the carbon particles are conductive. The surface
of the conductive rubber 706 is rough to some extent. As mentioned
above, unlike the dielectric substance 808 in the hard-type
electric pen, the other end face of the dielectric substance 708
facing the conductive rubber 706 is ground by a file No. 320.
Accordingly, a high exfoliation can be achieved after the
conductive rubber 706 contacts the other end face of the dielectric
substance 708. Moreover, because of the high flexibility of the
conductive rubber 706, the capacity of the variable capacity
condenser in the soft-type electric pen can be varied with a higher
touch.
The conventional hard-type and soft-type electric pens described
above have many components, including common components such as a
core bladder, an upper switching case, a lower switching case, and
pins for two electrodes. Because of these many components, the
manufacturing cost of the conventional electric pens is high. Also,
the conventional electric pens require many manufacturing and
assembly steps. Furthermore, the other diameter of the conventional
electric pens cannot be narrowed beyond a certain size because they
have to accommodate the upper and lower switching case.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a variable
capacity condenser and a pointer that obviate one or more of the
limitations and disadvantages of prior art variable capacity
condensers and pointers. The advantages and purposes of the
invention will be set forth in part in the description which
follows, and in part will be obvious from the description, or may
be learned by practice of the invention. The advantages and
purposes of the invention will be realized and attained by the
elements and combinations particularly pointed out in the appended
claims.
To attain the advantages and in accordance with the purposes of the
invention, as embodied and broadly described herein, the invention
is directed to a variable capacity condenser comprising a
dielectric substance, two electrodes, and a flexible electrode. The
dielectric substance has two end faces. The two electrodes are
disposed on one end face of the dielectric substance. The flexible
electrode faces the other end face of the dielectric substance. The
flexible electrode is pressible by a pressing member to vary a
distance between at least a portion of the flexible electrode and
the other end face of the dielectric substance.
In another aspect, the invention is directed to a pointer
comprising a casing, a circuit, and a pressing member. The circuit
is disposed within the casing. The circuit includes a variable
capacity condenser comprising a dielectric substance, two
electrodes, and a flexible electrode. The dielectric substance has
two end faces. The two electrodes are disposed on one end face of
the dielectric substance. The flexible electrode faces the other
end face of the dielectric substance. The pressing member presses
the flexible electrode of the variable capacity condenser to vary a
distance between at least a portion of the flexible electrode and
the other end face of the dielectric substance.
It is to be understood that both the foregoing general description
and the following detailed description are exemplary and
explanatory only and are not restrictive of the invention, as
claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute
a part of this specification, illustrate several embodiments of the
invention and together with the description, serve to explain the
principles of the invention. In the drawings,
FIG. 1 is a sectional view of an exemplary electric pen according
to the present invention showing the components of a variable
capacity condenser in an exploded view;
FIG. 2 is a sectional view of another exemplary electric pen
according to the present invention showing the components of a
variable capacity condenser in an exploded view;
FIG. 3 is a sectional view of yet another exemplary electric pen
according to the present invention showing the components of a
variable capacity condenser in an exploded view;
FIG. 4 is a sectional view of yet another exemplary electric pen
according to the present invention showing the components of a
variable capacity condenser in an exploded view;
FIG. 5 is a sectional view of yet another exemplary electric pen
according to the present invention showing the components of a
variable capacity condenser and a pressing member in an exploded
view;
FIG. 6 is a sectional view of a circuit substrate and a dielectric
substance according to the present invention illustrating their
soldered connection;
FIG. 7 is a section view of a conventional soft-type electric pen
showing the components of a variable capacity condenser in an
exploded view;
FIG. 8 is a section view of a conventional hard-type electric pen
showing the components of a variable capacity condenser in an
exploded view;
FIG. 9 is a graph showing a tool force-load property of an electric
pen according to the present invention;
FIG. 10 is a graph showing a tool force-load property of a
conventional soft-type electric pen; and
FIG. 11 is a graph showing a tool force-load property of a
conventional hard-type electric pen.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the presently preferred
embodiment of the present invention, examples of which are
illustrated in the accompanying drawings.
In accordance with the present invention, there is provided a
pointer comprising a casing, a circuit, and a pressing member. The
circuit is disposed within the casing. The circuit includes a
variable capacity condenser comprising a dielectric substance, two
electrodes, and a flexible electrode. The dielectric substance has
two end faces. The two electrodes are disposed on one end face of
the dielectric substance. The flexible electrode faces the other
end face of the dielectric substance. The pressing member presses
the flexible electrode of the variable capacity condenser to vary a
distance between at least a portion of the flexible electrode and
the other end face of the dielectric substance.
In the illustrated embodiment shown in FIG. 1, a pointer is an
electric pen comprising an electric pen casing 101, a circuit
substrate 114, a variable capacity condenser to be described in
more detail below, and a coil 103. Except for a pen point of a core
102 protruding outside the electric pen casing 101, all components
of the electric pen are disposed within the electric pen casing
101.
The electric pen includes a resonance circuit, which cooperates
with a pointing device, such as a tablet (not shown), to input a
coordinate as well as a tool force of the electric pen into a
computer (not shown). A tablet typically includes a flat input
surface having many loop coils arranged in parallel and in every
direction. The tablet detects and inputs into a computer a
coordinate position as well as a tool force of the electric pen by
an electromagnetic exchange between the resonance circuit of the
electric pen and a loop coil in the tablet. In the illustrated
embodiment shown in FIG. 1, a resonance circuit mainly comprises a
fixed condenser 113 provided with the circuit substrate 114, a
variable capacity condenser to be described in more detail below,
and the coil 103.
In the illustrated embodiment shown in FIG. 1, a variable capacity
condenser comprises a dielectric substance 118 having two end
faces, two electrodes 119 and 120 disposed on one end face of the
dielectric substance 118, and a conductive rubber 117 facing the
other end face of the dielectric substance 118. The conductive
rubber 117 is flexible and functions as an electrode of the
variable capacity condenser. The variable capacity condenser
illustrated in FIG. 1 have two condensers, one between the
electrode 119 and the conductive rubber 117 and another between the
electrode 120 and the conductive rubber 117. Therefore, the
integrated capacity of the variable capacity condenser is obtained
between the electrode 119 and the electrode 120. Preferably, the
two electrodes 119 and 120 are semicircular disks disposed on one
end face of the dielectric substance 118 by baking. As shown in
FIG. 1, the one end face of the dielectric substance 118 includes a
portion separating the two electrodes 119 and 120 by a
predetermined distance.
As illustrated in FIGS. 1 and 6, the circuit substrate 114 is an
elongated rectangle disposed in the longitudinal direction of the
electric pen casing 101. The circuit substrate 114 has an end face
abutting the dielectric substance 118 at the portion separating the
two electrodes 119 and 120. Preferably, the thickness of the
circuit substrate 114 is substantially the same as the
predetermined distance of the portion of the dielectric substance
118 separating the two electrodes 119 and 120.
The circuit substrate 114 is a double-sided substrate having front
and back sides. Each of the front and back sides of the circuit
substrate 114 has a portion of the resonance circuit printed
thereon. Each portion of the resonance circuit printed on the front
and back sides of the circuit substrate 114 includes a conducting
portion. The conducting portions provided on the front and back
sides of the circuit substrate 114 are electrically connected to
two electrodes 119 and 120, respectively.
The conducting portions are preferably provided around the end face
of the circuit substrate 114 abutting the dielectric substance 118
and are electrically connected to the two electrodes 119 and 120 by
soldering as illustrated in FIG. 6. In addition to electrically
connecting the conducting portions to the two electrodes 119 and
120, solders 125 and 126 mechanically connect the circuit substrate
114 to the dielectric substance 118 and maintain the circuit
substrate 114 perpendicular to the one end face of the dielectric
substance 118. To maintain the circuit substrate 114 stationary, a
portion of the inner configuration of the electric pen casing 101
presses the other end face of the circuit substrate 114 opposite
from the end face abutting the dielectric substance 118.
In the illustrated embodiment shown in FIG. 1, the core 102 is made
integral with a ferrite core 123 around which the coil 103 is
wound. Thus, when pressure is applied to the pen point of the core
102 protruding outside the electric pen casing 101, the pen point
of the core 102 transmits the pressure to the ferrite core 123. The
ferrite core 123 then presses the conductive rubber 117 toward the
other end face of the dielectric substance 118 and decreases the
distance between a portion of the conductive rubber 117 and the
other end face of the dielectric substance 118. A portion of the
conductive rubber 117 contacts the other end face of the dielectric
substance 118 and the contact area increases as the pressure
applied to the pen point increases. As the contact area increases,
the air disposed between the conductive rubber 117 and the other
end face of the dielectric substance 1188 is expelled.
Consequently, the capacity of the variable capacity condenser
changes as less air contributes as a dielectric material.
Therefore, the integrated capacity of the variable capacity
condenser varies slightly depending on the amount of pressure
applied to the pen point. This varying capacity in turn slightly
vary the resonance frequency of the resonance circuit. A pointing
device (e.g., a tablet) detects the variance of the resonance
frequency of the resonance circuit. FIG. 9 shows a tool force-load
property of an electric pen according to the present invention.
In the illustrated embodiment shown in FIG. 1, the ferrite core 123
is a cylindrical column made of L6 member and has an outer diameter
of 4.0 mm and a length of 17.5 mm. The coil 103 is a wire made of a
Litz line 2-ULAP7/0.07 wound around the ferrite core 123 thirty
eight turns in the first layer and thirty five turns in the second
layer. The first layer of the coil 103 contacts the surface of the
ferrite core 123 while the second layer of the coil 103 is wound
around the first layer. Both the first and second layers of the
coil 103 are wound without any gaps between the turns. The coil 803
has an inductance L=100 .mu.H, Q=200 (a frequency of 500 kHz). The
dielectric substance 118 employs a titanic acid strontium system
and has an outer diameter of 4 mm and a thickness of 1 mm. The
conductive rubber 117, comprising a mixture of synthetic rubber and
conductive particles, has a thickness of 0.4 mm and an outer
diameter of 4.0 mm. Preferably, carbon particles are used as the
conductive particles. The surface of the conductive rubber 706 is
rough to some extent. The one end face of the dielectric substance
118 facing the conductive rubber 117 is ground using a file No.
320.
FIG. 2 illustrates another embodiment of an electric pen having a
variable capacity condenser. In the illustrated embodiment shown in
FIG. 2, a combination of a deposition film 222 and a silicon rubber
221 replaces the conductive rubber 117 shown in FIG. 1. The silicon
rubber 221 is positioned between the deposit film 222 and a ferrite
core 223. As the deposition film 222, UPILEX.TM. of 75 micrometers
can be utilized. Nickel chrome having a thickness of 1000 angstroms
is deposited on the deposit film 222. The silicon rubber 221 has a
thickness of 0.4 mm and an outer diameter of 4.0 mm. All other
aspects of this embodiment are the same as those shown in FIG.
1.
FIG. 3 illustrates yet another embodiment of an electric pen having
a variable capacity condenser. In the illustrated embodiment shown
in FIG. 3, a spacer 307 is added to the embodiment shown in FIG. 1.
The spacer 307 is positioned between a conductive rubber 317 and
the other end face of the dielectric substance 318. Depending on
the inductance of a coil 303 and the capacity of a condenser 313,
this embodiment including the spacer 307 may be appropriate.
Furthermore, the extent of the roughness in the other end face of a
dielectric substance 318 facing the conductive rubber 317
determines whether the spacer 307 is necessary or not. All other
aspects of this embodiment are the same as those shown in FIG.
1.
FIG. 4 illustrates yet another embodiment of an electric pen having
a variable capacity condenser. In the illustrated embodiment shown
in FIG. 4, a spacer 407 is added to the embodiment shown in FIG. 2.
The spacer 407 is positioned between a deposit film 422 and the
other end face of a dielectric substance 418. All other aspects of
this embodiment are the same as those shown in FIG. 2.
FIG. 5 illustrates yet another embodiment of an electric pen having
a variable capacity condenser. In the illustrated embodiment shown
in FIG. 5, a core 502 slides through a hollow cylindrical ferrite
core 523. Therefore, the back side of the core 502 instead of the
back side of the ferrite core 523 presses a conductive rubber 517
toward the other end face of a dielectric substance 518. The back
side of the core 502, which is greater than the inner diameter of
the ferrite core 523, prevents the core 502 from disengaging from
the ferrite core 503. All other aspects of this embodiment are the
same as those shown in FIG. 1.
Employing the variable capacity condenser of the present invention
describes the number of components to be contained within an
electric pen. Fewer components in turn decrease the manufacturing
cost of an electric pen. Specifically, the present invention
eliminates the need to contain upper and lower switching cases and
their related pins in an electric pen housing by disposing two
electrodes on one end face of a dielectric substance and
electrically connecting them to conduction portions of a resonance
circuit provided on a circuit substrate.
In addition, the variable capacity condenser of the present
invention can be contained in a narrow electric pen casing because
fewer components are needed. Because the variable capacity
condenser of the present invention does not need upper and lower
switching cases and their related pins, an inner diameter of an
electric pen casing needs to be only slightly larger than the outer
diameter of a dielectric substance. Thus, for a given thickness of
an electric pen casing, an outer diameter of an electric pen casing
can be narrower than that of a conventional electric pen casing.
For example, if the outer diameter of a dielectric substance is 4
mm and the thickness of an electric pen casing is about 1.25 mm,
the outer diameter of the electric pen casing can be about 6.5 mm
because the inner diameter of an electric pen casing needs to be
slightly larger than 4 mm. However, given the same outer diameter
of a dielectric substance and the same thickness of an electric pen
casing, a conventional electric pen cannot have the outer diameter
of an electric pen casing about 6.5 mm because it has to
accommodate upper and lower switching cases and their related
pins.
It will be apparent to those skilled in the art that various
modifications and variations can be made in the assembly of the
present invention without departing from the scope or spirit of the
invention. Other embodiments of the invention will be apparent to
those skilled in the art from consideration of the specification
and practice of the invention disclosed herein. It is intended that
the specification and examples be considered as exemplary only,
with a true scope and spirit of the invention being indicated by
the following claims.
* * * * *