U.S. patent number 3,860,771 [Application Number 05/410,329] was granted by the patent office on 1975-01-14 for keyboard switch assembly with dome shaped actuator having associated underlying contactor means.
This patent grant is currently assigned to Chomerics, Inc.. Invention is credited to William J. Lynn, Richard E. Seeger.
United States Patent |
3,860,771 |
Lynn , et al. |
January 14, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
KEYBOARD SWITCH ASSEMBLY WITH DOME SHAPED ACTUATOR HAVING
ASSOCIATED UNDERLYING CONTACTOR MEANS
Abstract
A keyboard device utilizing a conductive plastic material layer
which contacts circuit elements or pathways, the improvement of
snapable plastic means raised on a pedestal through which it snaps
through center to provide a feel of completion of circuit contact
to the user.
Inventors: |
Lynn; William J. (Groveland,
MA), Seeger; Richard E. (Topsfield, MA) |
Assignee: |
Chomerics, Inc. (Woburn,
MA)
|
Family
ID: |
23624255 |
Appl.
No.: |
05/410,329 |
Filed: |
October 29, 1973 |
Current U.S.
Class: |
200/5A; 200/1R;
200/262; 200/302.2; 200/513; 400/479; 200/5R; 200/265; 200/329;
200/333; 235/145R; 400/491.3 |
Current CPC
Class: |
H01H
13/702 (20130101); H01H 13/785 (20130101); H01H
1/029 (20130101); H01H 2215/008 (20130101); H01H
2207/012 (20130101); H01H 2215/002 (20130101); H01H
2229/032 (20130101); H01H 2215/006 (20130101); H01H
2227/022 (20130101); H01H 2201/026 (20130101); H01H
2205/002 (20130101); H01H 2223/036 (20130101); H01H
2201/032 (20130101); H01H 2227/012 (20130101); H01H
2209/002 (20130101); H01H 2229/026 (20130101); H01H
2229/05 (20130101); H01H 2227/002 (20130101); H01H
2219/028 (20130101) |
Current International
Class: |
H01H
13/70 (20060101); H01H 1/029 (20060101); H01H
13/702 (20060101); H01H 1/02 (20060101); H01h
013/70 (); H01h 001/02 () |
Field of
Search: |
;200/1R,5R,5A,16A,DIG.1,67DA,67DB,76,159R,159A,159B,166C,166PC,172R
;197/98-103 ;235/145R ;340/365R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
IBM Technical Disclosure Bulletin, Kuntzleman, "Keyboard
Transducer," Vol. 7, No. 12, p. 1170, May 1965. .
IBM Technical Disclosure Bulletin, Sedaris et al., "Elastic
Diaphragm Switch," Vol. 14, No. 3, p. 767, August 1971. .
Flex Key Data Bulletin DK-1, "Flex Key Integrated Decimal Keyboard
Units," published 1970..
|
Primary Examiner: Scott; James R.
Attorney, Agent or Firm: Dike, Bronstein, Roberts, Cushman
& Pfund
Claims
We claim:
1. A keyboard assembly comprising first means for supporting an
electrically conductive contact means, electrically conductive
contactor means positioned over but out of electrical contact with
said contact means, support means for positioning said conductive
contact or means over but out of electrical contact with said
contact means a flexible and resilient plastic sheet means
positioned above said conductive contactor means and having formed
therein a plurality of raised protrusions positioned at the center
thereof farthest from said conductive contact means, said
protrusions each comprising a pedestal and a curved surface capping
said pedestal, said curved surface being depressable at its center
under pressure below the pedestal to push said conductive contactor
means against said contact means and snapping through the center
upon depression sufficient to cause electrical contact between said
conductive contactor means and said contact means, and said curved
surface recovering back through the center after pressure is
withdrawn therefrom and a snap through layer positioned between
said sheet means and said conductive contact or means, said snap
through layer having a plurality of openings therethrough in
register with said protrusions, said protrusions extending into
said openings upon depression through center sufficient to cause
contact between said contactor means and contact means.
2. A keyboard according to claim 1, in which said support means
comprises a separator layer is positioned between said contactor
means and contact means, said separator layer having a plurality of
openings each in register with a different one of said protrusions
and each in exposing portions of said contact means for contact
with said contactor means.
3. A keyboard according to claim 2 in which said snap through layer
which is positioned between said contactor means and said sheet
means has its plurality of openings each in register with a
different one of said protrusions and with a different one of said
openings of said separator layer.
4. A keyboard according to claim 3 in which a spring loaded button
assembly comprising a plurality of buttons is provided to depress
said protrusions, a different one of said buttons positioned to
depress a different one of said protrusions, and wherein means is
provided for supporting said button assembly over said sheet means
and its protrusions.
5. A keyboard according to claim 4 in which the conductive
contactor means comprises an elastomeric conductive layer.
6. A keyboard according to claim 3 in which the conductive
contactor means comprises an elastomeric conductive layer.
7. A keyboard according to claim 1 in which the conductive
contactor means comprises a flexible plastic conductive layer.
8. A keyboard according to claim 1 in which the pedestal is
cylindrical in shape.
9. A keyboard according to claim 1 in which the curved surface is a
portion of a sphere.
10. A keyboard according to claim 9 in which the pedestal is
cylindrical in shape.
11. In a keyboard according to claim 1 including a plurality of
spring loaded buttons for depressing said protrusions, and means
for supporting said buttons over said protrusions.
12. A keyboard assembly comprising first means for supporting an
electrically conductive contact means, electrically conductive
contactor means positioned above but out of electrical contact with
said electrically conductive contact means, a plastic sheet means
positioned above said conductive contactor means and having formed
therein a plurality of raised flexible and resilient protrusions
positioned farthest at their centers from said conductive contact
means, said protrusions each comprising a pedestal and a curved
surface capping said pedestal, said curved surface being
depressable under pressure below said pedestal to push said
conductive contactor means against said contact means and snapping
through center upon depression sufficient to cause electrical
contact between said conductive contactor means and said contact
means, and said curved surface recovering back through the center
after pressure is withdrawn therefrom and said electrically
conductive contactor means supported on the under surface of said
curved surface.
13. A keyboard assembly according to claim 12 in which a snap
through layer is positioned between said sheet means and said
conductive contact means, said snap through layer having a
plurality of openings therethrough in register with said
protrusions, said protrusions extending into said openings upon
depression sufficient to cause contact between said contactor and
contact means.
14. A keyboard according to claim 13 in which a spring loaded
button assembly comprising a plurality of buttons is provided to
depress said protrusions, a different one of said protrusions by a
different one of said buttons, and means for supporting said button
assembly over said sheet and its protrusions.
15. A keyboard assembly according to claim 13 in which the
conductive contactor means extends over the sheet means and is
supported thereby for movement with the under surface of the
pedestal and the curved surface.
16. A keyboard assembly according to claim 13 in which the
conductive contactor means is in the shape of a circuit pattern
supported by the sheet means with portions thereof extending into
the protrusions and supported by the under surface of the pedestal
and the curved surface for movement therewith.
17. A keyboard according to claim 12 in which a spring loaded
button assembly comprising a plurality of buttons is provided to
depress said protrusions, a different one of said buttons
positioned to depress a different one of said protrusions, and
means for supporting said button assembly over said sheet and its
protrusions.
18. A keyboard assembly according to claim 12 in which the flexible
plastic conductive layer is confined to the under surface of said
curved surface.
19. A keyboard assembly according to claim 12 including indicia
formed in, on, or supported by said protrusion curved surface.
20. A keyboard assembly comprising first means for supporting an
electrically conductive contact means, electrically conductive
contactor means positioned above but out of electrical contact with
said contact means a plastic sheet means positioned above said
conductive contactor means and having therein a plurality of
flexible and resilient raised protrusions positioned farthest from
said conductive contact means said protrusions each comprising a
curved surface which at its uppermost point is farthest from said
contact means said curved surface being depressable under pressure
to push said conductive contactor means against said contact means
and snapping through the center and inverting upon depression
sufficient to cause electrical contact between said conductive
contactor means and said contact means, said surved surface
recovering back through the center after pressure is withdrawn
therefrom, said electrically conductive contact means supported on
the under surface of said curved surface.
21. A keyboard assembly according to claim 20 in which a snap
through layer is positioned between said sheet means and said
conductive contact means, said snap through layer having a
plurality of openings therethrough in register with said
protrusions, said protrusions extending into said openings upon
depression sufficient to cause contact between said contactor and
contact means.
22. A keyboard according to claim 21 in which said protrusions also
include a substantially cylindrical pedestal which supports said
curved surface on the top thereof.
23. A keyboard according to claim 22 in which a spring loaded
button assembly comprising a plurality of buttons is provided to
depress said protrusions, a different one of said buttons
positioned to depress a different one of said protrusions, and
means for supporting said button assembly above said
protrusions.
24. A keyboard according to claim 22 in which the conductive
contactor means comprises a flexible insulator filled with
electrically conductive particles.
25. A keyboard according to claim 20 in which said protrusions also
include a substantially cylindrical pedestal which supports said
curved surface on the top thereof.
26. A keyboard according to claim 20 in which the conductive
contactor comprises an elastomeric insulator material filled with
electrically conductive particles.
27. A keyboard according to claim 20 in which the conductive
contactor comprises a flexible plastic insulator material filled
with electrically conductive particles.
28. A keyboard according to claim 20 in which the curved portion is
a portion of a sphere.
29. In a keyboard according to claim 20 including a plurality of
spring loaded buttons for depressing said protrusions and means for
supporting said buttons over said protrusions.
30. A keyboard assembly comprising a circuit board for supporting
an electrically conductive circuit having contact means,
electrically conductive contactor means positioned above but out of
electrical contact with said contact means, a sheet means of
insulator plastic material positioned above said conductive
contactor means and having therein a plurality of raised
protrusions positioned farthest from said conductive contact means,
said protrusions each comprising a curved surface, said curved
surface being depressable under pressure to push said conductive
contactor means against said contact means and snapping through the
center and inverting upon depression sufficient to cause electrical
contact between said conductive contactor means and said contact
means, and said curved surface recovering back through the center
after pressure is withdrawn therefrom, said electrically conductive
contactor means supported on the under surface of said curved
surface.
31. A keyboard assembly according to claim 30 in which a snap
through layer is positioned between said sheet means and said
conductive contact means, said layer having a plurality of openings
therethrough in register with said protrusions, said protrusions
extending into said openings upon depression sufficient to cause
contact between said contactor and contact means.
32. A keyboard according to claim 31 in which a spring loaded
button assembly comprising a plurality of buttons is provided to
depress said protrusions, a different one of said protrusions by a
different one of said buttons, and means for supporting said
buttons over said protrusions.
33. A keyboard according to claim 30 in which a spring loaded
button assembly comprising a plurality of buttons is provided to
depress said protrusions, a different one of said buttons
positioned to depress a different one of said protrusions, and
means for supporting said buttons over said protrusions.
34. A keyboard assembly according to claim 30 in which the
contactor means comprises a flexible plastic conductive material
which extends over the sheet means and is supported thereby on the
under surface thereof.
35. A keyboard assembly according to claim 30 in which the
contactor means comprises flexible plastic conductive material
confined to the curved surface.
36. A keyboard assembly according to claim 30 in which the
contactor means comprises flexible plastic conductive material in
the shape of a circuit pattern is supported by the under surface of
the sheet means with portions thereof supported by the curved
surface for movement therewith.
37. A keyboard assembly according to claim 30 including indicia
formed in, on, or supported by said protrusion curved surface.
38. A keyboard assembly comprising first means for supporting
electrically conductive contact means, an insulator spacer having a
plurality of openings in register with selected portions of said
contact means, electrically conductive contactor means positioned
over said insulator spacer, a snap through insulator material layer
positioned over said electrically conductive contactor means and
having openings therethrough in register with the opening of said
spacer, and a sheet means of insulator plastic material positioned
over said snap through layer and having a plurality of raised
protrusions in register with the openings of the snap through layer
and comprising a curved surface, said curved surface being
depressable and inverting under pressure to extend through the
openings of said snap through layer to engage said contactor means
to force same through said openings of the spacer to electrically
contact the contact means.
39. A keyboard assembly according to claim 38 in which a spring
loaded button assembly comprising a plurality of buttons is
provided to depress said protrusions, a different one of said
protrusions by a different one of said buttons, and means for
supporting said buttons over said protrusions.
40. A keyboard assembly comprising support means, electrically
conductive contact means supported by said support means, an
insulator material snap through layer having one side thereof
positioned over said conductive contact means, said snap through
layer having a plurality of openings therethrough in register with
portions of said electrically conductive contact means, a sheet of
flexible and resilient insulator plastic material positioned on the
opposite side of said snap through layer, said sheet having formed
therein a plurality of raised protrusions which extend above said
sheet and away from said snap through layer, each of said
protrusions comprising a curved surface and each of said
protrusions in register with a different one of said openings of
said snap through layer, electrically conductive circuit pattern
means adhered to the side of the sheet closest to said snap through
layer and having portions thereof extending into the protrusions
and adhering to the under surface of the curved surface and
providing contactor means so that upon depression of said
protrusions said protrusions snap through center and invert into
said openings of said snap through layer and position said
contactor means against said contact means.
41. A keyboard assembly according to claim 40 in which said
protrusions each comprises a pedestal supporting said curved
surface on the top thereof and in which the circuit pattern means
also adheres to the under surface of the pedestal.
42. A keyboard assembly according to claim 41 in which said circuit
pattern is of a flexible conductive plastic material.
43. A keyboard assembly according to claim 42 in which there is
provided a plurality of buttons for depressing said curved surface,
and in which there is provided means for supporting said buttons
over different ones of said protrusions to depress said curved
surface thereof.
44. A keyboard assembly according to claim 40 in which said circuit
pattern is of a flexible conductive plastic material.
45. A keyboard assembly according to claim 44 in which there is
provided a plurality of buttons for depressing said curved surface,
and in which there is provided means for supporting said buttons
over different ones of said protrusions to depress said curved
surface thereof.
46. A keyboard assembly according to claim 1 including indicia
formed in, on, or supported by said protrusion curved surface.
Description
BACKGROUND OF THE DISCLOSURE
This invention is directed a a new, improved and inexpensive method
to manufacture (in comparison with the prior art) keyboard devices
which include new and improved means to effect the users sense of
feel so as to provide the user with confidence that electrical
connection has been made.
Within the last few years the personal calculator market has
mushroomed with the result that many manufacturers have entered the
business. With numerous manufacturers competing for the same
market, the price of culculators have begun to decrease
rapidly.
Accordingly, as prices fell, calculator manufacturers looked for
ways to cut their manufacturing and component part costs.
In order to attempt to satisfy the cost reduction efforts of
calculator manufacturers, keyboard manufacturers also had to
develop new and improved techniques to reduce their manufacturing
and parts costs.
The present invention represents the results of one such effort in
cost reduction and provides less costly to manufacture keyboards in
comparison with other keyboards previously and presently offered by
the assignee of this application. For example, see U.S. Pat. Nos.
3,705,276, 3,721,778, 3,780,237, and 3,773,998, and application on
file in the U.S. Patent Office and assigned to Chomerics, Inc.
Attention is also directed to U.S. Pat. Nos. 3,699,294, 3,707,609,
3,120,583, 3,600,528, 3,594,684 and 3,476,972 among many others
which disclose other keyboard configurations.
BRIEF SUMMARY OF THE DISCLOSURE
This invention is directed to a keyboard in various configurations
for providing an encoded signal representative of key depression.
As part of this keyboard there is provided a resilient and flexible
material layer in which there is provided a plurality of raised
buttons, e.g., a cylindrical pedestal having straight or sloped
walls topped or capped by a portion of a curved surface e.g., a
portion of a sphere.
In the preferred embodiment, indicia, e.g., numbers, letters, or
symbols are printed on the curved surfaces so that they may be seen
by the user. In the preferrred embodiment, the raised protrusions
not only carry the indicia of the keyboard but also act and feel
like snap acting keys when depressed although they are many times
less costly to manufacture.
In other configurations the sheet having the plurality of
protrusions is used in conjunction with a key to provide the key or
button user with the snap action indicative of contact closure.
As another feature of this invention, it has been determined that a
better snap action is obtained if a separator or snap through layer
of material (insulator) having a plurality of holes or openings
(about the same size as the bottom of the pedestal) is positioned
immediately below the layer carrying the protrusions with each
opening in register with a different one of the pedestal
bottoms.
It has been found that with the separator layer, the curved
surfaces snap better through the center upon depression and feels
more like the depression of a key.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a keyboard according to this disclosure
with parts broken away;
FIG. 2 is a top view illustrating a plurality of snap action
protrusions in a sheet of the keyboard;
FIG. 3 is a top view of the first and second separator sheet of the
device of FIG. 1;
FIG. 4 is a sectional view taken along line 4--4 in FIG. 3;
FIG. 5 is a sectional view taken along line 5--5 in FIG. 1
illustrating the moving parts of the keyboard before being
depressed;
FIG. 6 is a sectional view of the keyboard illustrating the moving
parts of the keyboard after being depressed;
FIG. 7 illustrates in a sectional view taken similarly to FIG. 5
another embodiment of the keyboard;
FIG. 8 illustrates in a sectional view taken similarly to FIG. 5
another embodiment of the keyboard;
FIG. 9 illustrates in a bottom view the contactor means of the
keyboard of FIG. 8;
FIG. 10 is a sectional view taken along line 10--10 of FIG. 9;
FIG. 11 illustrates in a bottom view the sheet with protrusions
supporting an isolated layer of electrically conductive contactor
means;
FIG. 12 is a sectional view taken along line 12--12 of FIG. 11;
FIG. 13 is a sectional view taken similarly to FIG. 5 illustrating
the contactor means and sheet shown in FIGS. 11 and 12;
FIG. 14 is a bottom view of the sheet with protrusions covered by a
layer of electrically conductive contactor means;
FIG. 15 is a sectional view taken along line 15--15 of FIG. 14;
FIG. 16 is a sectional view similar to FIG. 5 illustrating the
coated sheet of FIGS. 14 and 15 in the keyboard;
FIG. 17 is a bottom view of the sheet with protrusions covered by a
layer of conductive circuitry or circuit pattern for making contact
with contact elements of a circuit board;
FIG. 18 is a sectional view taken along line 18--18 of FIG. 17;
FIG. 19 illustrates in a sectional view a modified keyboard using a
button to depress the protrusions of the sheet;
FIGS. 20 and 21 illustrates in a top and bottom view an apparatus
suitable for forming the protrusions in the sheet of the FIGS;
FIG. 22 illustrates the protrusion being formed in the plastic
sheet; and
FIG. 23 illustrates in a sectional view similar to FIG. 5, a
keyboard constructed of a sheet means having a plurality of curved
protrusions without a pedestal.
DETAILED DESCRIPTION OF THE DISCLOSURE
Reference should now be had to FIGS. 1-6 for a description of a
keyboard embodying the invention. In these FIGS. a keyboard is
disclosed as having a frame 30 e.g., of a plastic, e.g.,
polysterene; polypropylene or other high impact plastics well known
in the art.
The frame is open at the bottom and is provided with a plurality of
windows or openings 31 and a plurality of rods 32 extending
downwardly. Heads 32a may be formed by heat depending on the
plastic used as shown in FIGS. 5 and 6 to hold the layers to be
described of the keyboard together as a unit. Alternatively the
rods may be threaded and nuts may be used to do likewise.
Positioned below the frame top is a layer 35 preferably of a
flexible and resilient plastic having a plurality of raised
protrusions formed with a curved snapable portion 35a capping or on
top of a pedestal 35 preferably cylindrically shaped although
obviously its shape can vary somewhat so long as its side walls can
easily spread outwardly as the snapable portions pass through the
center (see FIG. 6).
The plastic layer 35 may be of thermoplastic or thermosetting
flexible and resilient plastic materials such as polyester e.g.
Mylar, polypropylene, polyethelene, silicone rubbers, polyurethane,
etc.
Positioned below the snapable layer there is preferably provided a
snap through layer 36 e.g., of insulator material such as Mylar,
having a plurality of windows or holes 36a of about the same size
as the pedestal 35b bottom.
The snap through layer is used to provide the total feel of snap
through by giving the snapable portion 35a enough room to fully
invert. It should be understood that the snap through layer 35 is
not necessary but is preferred to provide the best tactile feel in
most cases.
Below the snap through layer is an elastomeric conductive plastic
layer such as of silicone rubber filled with conductive particles
such as silver as shown in U.S. Pat. No. 3,721,778 or in the
aforementioned applications.
Other well known conductive particles such as carbon, gold, or
composites thereof may be used as is well known in the art.
Positioned below the conductive plastic layer 37 is an insulator
material separator layer 38 e.g., Mylar, polyethylene having the
same configuration as the layer 36 in FIG. 3 and also having a
plurality of holes or windows 38a which the elastomeric conductive
layer 37 may be forced.
At 49 there is shown a typical circuit board e.g., of Bakelite
having a conductive pattern 39 supported thereby. The conductive
pattern may be etched copper or a conductive ink.
In this embodiments shown in FIG. 5 connecting pins are shown at 41
and 42 for making electrical contact with the conductive plastic
layer 37 as well as the circuit pattern 39.
In FIG. 6 there is shown pressure (by a finger) being applied to
the snapable portion 35a and forcing it to snap through center to
force the conductive plastic layer 37 through the separator 38 and
into contact with one or more elements or pathways of the circuit
pattern 39.
Various circuit patterns may be observed in the aforementioned U.S.
Pat. Nos. 3,705,276 and 3,721,778.
Upon release and removal of the finger, the protrusions comprising
the snapable members 35a and pedestal 35b return to the unflexed
position shown in FIG. 5 with the electrically conductive contactor
or conductive plastic layer 37 also returning as shown.
Indicia such as numbers may be applied to the snapable portion 35a
by printing techniques well known in the art or even paste-on
numbers may be applied thereto. Thus the snapable members look like
keys to the user. In practice it has been found that the layer with
protrusions may comprise a 5 mil sheet of Mylar with the pedestal
height t.sub.p being 10 mils and the curved portion height being 21
mils and the pedestal bottom having a diameter of about 3/8 inch.
The curved portion is a portion of a sphere having a 700 mil
radius.
In FIG. 7 there is shown an alternate embodiment of the disclosure
in that a composite contactor is formed of an elastomeric
non-electrically conductive layer and a thin flexible conductive
layer such as of a polyamide filled or loaded with conductive
particles.
The elastomeric layer may be rubber such as silicone, nitrile,
etc., and the flexible conductive layer may be of a polyamide
adhesive e.g., Versalon 1140 by General Electric or others such as
polyester, e.g., Mylar, filled with silver particles e.g., 20 to 40
volume percent. The thickness of the elastomeric layer may vary
between 5 to 200 mils with about 20 mils being convenient and the
flexible conductive layer 51 is preferably between 5 microns to
about 2 mil in thickness with about 10 to 25 microns being
preferred.
Since the remaining parts in this embodiment is the same, the same
numbers designate like parts. In FIGS. 8-10 there is shown still a
further embodiment with like parts being given like numeral
designations.
In this embodiment the electrical contact is made between portions
of a conductive pattern or conductive pathways 61 and portions or
elements of the circuit board supported circuit pattern 39.
The conductive pattern is supported by an elastomeric layer 60. The
pattern 61 may be sprayed on through a stencil to form the pattern
61.
The flexible conductive plastic material used for the layer 61 is
the same as the material used for the layer 51 and the elastomeric
layer is also of the same material as layer 50.
FIGS. 11-13 illustrate yet another embodiment of the invention. In
this embodiment as well as the embodiments shown in FIGS. 14-18,
the elastomeric or flexible layers (conductive or non-conductive)
as shown in FIGs. 1-10 are not used.
In FIGS. 11-13 the layer 35 supports layers of flexible
electrically conductive plastic material 70 on the underside of the
snapable members 35a. The layers 70 adhere thereto for movement
with the snapable portions 35a. The flexible conductive plastic
material may comprise a thin plastics such as epoxies, e.g., Nazdar
Co. BE-170 epoxy; polyesters, e.g., General Formulation, Div. of
General Research Inc. No. 140-1303. In addition adhesives may also
be used to provide adherence of the layer 70 to the layer 35 with
the above or other flexible conductive plastics.
The layer 70 is filled with electrically conductive particles such
as silver, gold, carbon, etc., and in a volume percent of between
10 to 80 percent with 20 to 40 volume percent being preferred.
The thickness of the layer 70 is preferably 5 microns to 1 mil with
5 microns to 12 microns being preferred. The layer 70 preferably
has a volume resistivity preferably less than 10 ohm cm, more
preferably below 1 ohm cm, and most preferably below .5 ohm cm. The
silver particles may be silflake 135 as is well known in the
art.
The flexible conductive plastic layer 70 may comprise other
materials such as polycarbonates (e.g., Lexan), epoxy (e.g.,
Corvel) polyacetate, polystyrine modified or unmodified by a
plastisizer to obtain the desired flexibility to flex with the
snapable members 35a and 35b.
A suitable formulation for the conductive layer 70 may comprise the
mixture of 20 parts by weight of the BE-170 epoxy above, 80 parts
by weight of Silflake 135. The formulation is then preferably
applied to the layer 35 before forming the protrusions as in FIGS.
20-22. The layer 70 may be applied to the layer 35 by knife coating
it, silkscreening it or spraying it through a mesh or stencil.
Thereafter the layer 70 is cured in an oven as is conventional in
the art.
The protrusions 35a are now preferably formed. Alternatively, the
layer 70 may be applied after the protrusions 35a are formed.
Organic solvents e.g., such as NAZ DARS 70-182 Retarder Thinner
conventional in the art may be added if desired to permit easy
application of the layer 70.
As may be seen in this embodiment of FIG. 13 the separator layer 38
is removed and the conductive pattern or elements 39 are separated
into isolated elements 39a and 39b with contact pins 42a and 42b
being coupled to them as shown.
Electrical contact is made between the layers 39a and 39b by the
layer 70 making contact with both after being depressed.
FIGS. 14-16 illustrate a further modification and in this
embodiment a layer of flexible conductive plastic material of the
same composition and thickness as layer 70 is supported by and
adheres to the layer 35.
Depression of the snapable member 35a again causes contact with the
board 40 supported conductive circuit pattern 39.
FIGS. 17 and 18 illustrate still another embodiment wherein a
flexible conductive plastic circuit pattern 85 is supported by and
adheres to the plastic layer 35. A pin is provided at 81 to make
electrical contact with a portion of the circuit pattern 85.
Thus the configuration of FIGS. 17 and 18 provides further
advantages in savings of material.
The material 85 is again the same as the flexible material 70 in
composition and thickness.
FIG. 19 illustrates a device such as in FIG. 1 using a button 91
supported in a modified frame 90 for depressing the snapable member
35a.
In this configuration, the button is merely the extension of a
users finger. The operation of this device is the same as
heretofore described. Obviously the other modifications of FIGS.
7-18 may be included in FIG. 19. In this FIG. like numbers are
again used to designate the same parts as shown in FIGS. 1-6.
In order to fabricate the flexible layer 35 protrusions comprising
the pedestal 35b and the curved portion 35a, the dies 95 and 96
shown in FIGS. 20-22 may be used. In this configuration shaped rods
95a are provided for mating with cavities 96a.
The plastic material 35 e.g., Mylar is placed between the metal
e.g., steel dies (see FIG. 22) and pressure and heat is applied for
a preset amout of time to form the protrusions. In practice it has
been found that with a Mylar layer 35 of a 5 mil thickness, a
temperature of about 210.degree. F with 3,000 lbs. pressure for 15
seconds is adequate to form the about 3/8 inch wide pedestal
(bottom opening) and curved portion.
In FIG. 23 there is shown a device similar to that shown in FIG. 5
except that in this case the sheet 35 is provided with protrusions
having only curved portions 35a and no pedestal 35b. In this case
the snap through layer 36 if used is preferably made thicker to
compensate for the lack of a pedestal. Although this configuration
is usable, the protrusions with a pedestal 35b are much preferred
because they give a better tactile or key like feel under
depression. Like numbers used herein designate like parts as in
FIG. 5. The modifications shown in FIGS. 7-19 may also be included
in the structure of FIG. 23.
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