Note: Descriptions are shown in the official language in which they were submitted.
1037~5
Rubber keyboards for keyed structures are not new.
Neither are rubber keyboards having electrically conductive
portions thereon. There are problems, however, associated
with the currently used keyboards as well as problems
associated with their production.
Prior art keyboards are manufactured by joining a
contact material, i.e., an electrically conductive material
which has been fashioned beforehand, with a keyboard which is
either made of non-conductive material or is coated with
non-conductive material.
In a particular method, a large number of small
contact members are press formed by molding in metal molds.
The contact members are thereafter affixed to the keyboard,
thus constituting a two-step method of manufacture which is
not only complicated but is time consuming. In order to `-
- overcome the difficulties attendant in such an operation,
this invention was conceived and reduced to practice.
This invention relates to a method of manufacturing
a keyboard which is useful in keying structures. More
particularly, this invention relates to a rubber keyboard
which is useful in keying structures such as miniature,
hand-held computers and calculators.
The method of this invention comprises layering a
flat fixed plate with a thin layer of electrically conductive
paint, masking a prefotmed insulating rubber keyboard, laying
the so masked keyboard on the conductive paint and applying
- pressure to the rubber keyboard to the extent that certain
portions of the rubber keyboard are pressed downwardly into
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contact with the electrically conductive paint.
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1037~75 ~ i
This invention also relates to an article of
manufacture which is produced by the method of this invention.
More particularly, this invention relates to an insulating
rubber keyboard which has certain designated areas upon its
planar surface which are coated with an electrically conductive
paint. ~ ~
Thus, in accordance with the present teachings, - ; -
a method of manufacturing a keyboard is provided wherein the
method comprises contacting a preformed rubber keyboard without - -
electrically conductive paint at specific locations on the ~
keyboard to form the conductive contact. The method includes
the steps of spreading a thin layer of electrically conductive
paint on a flat fixed plate, surmounting the electrically
conductive paint with a masking shield, surmounting the masking
shield with a preformed insulating rubber keyboard, contacting
the preformed insulated rubber keyboard with a pressure means - -
whereupon those portions of the preformed rubber keyboard .7. .'1'
which are not masked are forced downwardly into intimate
contact with the electrically conductive paint causing the
paint to adhere to the preformed rubber keyboard. The pressure
means is subsequently released and the electrically conductive
paint permitted to dry. '^
Pursuant to the above and other aspects, the
invention will now be described in greater detail.
In the drawings, FIG. 1 is a plan view of the
under portion of the finished keyboard showing the contact :
points 2A and the silicone rubber support material 4;
FIG. lA is a cross-sectional view of the key-
board taken along the plane A-A; ;
FIG. 2 is a top plan view of the masking shield -
3 with the requisite openings 7 through which the portion of
rubber 4A passes to reach the electrically conductive paint;
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1037875
FIGS. 3 and 4 show a cross-sectional view of the
keyboard taken along the plane A-A shown in FIG. 1 and the
apparatus used in manufacture during the various steps of
the manufacture;
FIG. 5 is a cross-sectional view along plane A-A
of the finished article showing the rubber support material 4
and the contact thereupon, 2A.
Referring now to the drawings wherein like reference
characters designate like or corresponding parts throughout
the figures thereof, there is shown in FIG. 3 a
cross-sectional view of a portion of the manufacturing apparatus
and article of this invention. The invention requires a
flat fixed plate 1 which is at least as wide as the width of
the rubber keyboard w}lich is to be manufactured. Layered on
the surface of the flat fixed plate is an electrically -~
- conductive paint Z. Shown above the components 1 and 2 are
components 3 and 4, which are shown in plan view in FIGS. Z
and 1, respectively. The component 3 is a masking shield
which protects the surfaces of the insulating rubber
keyboard 4 which are not to be coated with the electrically
conductive paint 2. The masking shield 3 is generally affixed
to the rubber keyboard before the whole is surmounted on the
electrically conductive paint surface, although the affixing
of the masking shield is not essential and the masking shield
can be placed directly on the paint surface and the rubber
keyboard thereafter placed thereon. The rubber keyboard 4
is preformed from a resilient material, which resilience is
necessary for the satisfactory operation of the finished part
as well as for the satisfactory operation of the instant
method. Note that the manufacture of the preformed rubber
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10378'75
keyboard itself is not part of this invention. Note also :
that the rubber keyboard is manufactured with small rubber
dimples 5 on its upper surface. These dimples correspond
directly with the rubber portion 4A which is to become -
the contact 2A.
Referring now to FIG. 4, there is shown a cross- -
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sectional view of the same portion of apparatus as is shown
in FIG. 3. The components 1, 2, 3 and 4 are in the proper
position for the application of pressure. The pressure is
supplied by a roller 6 which passes over the components 1 ~ -~
through 4 and causes the portions 4A to be pushed downwardly
into the conductive paint surface. Note that the rubber
dimples 5 enhance the pressure of the roller at that point -
thereby causing the portions 4A to reach the paint surface
without undue pressure on the remainder of the rubber keyboard `
that is not intended to be coated. Note also that the invention
is not restricted to that portion of the invention where the
roller is passed over the components 1 through 4. Contemplated
within the scope of the invention is the situation where the
components 1 through 4 are passed under a stationary roller, and
mass production can be accomplished under such conditions by -
providing the components in the form of a moving belt which is
later cut into segments.
Immediately after the passage of the roller, the
resilient rubber keyboakd, portion 4A, springs back to its
normal configuration and the portion 4A is now coated with ~-
the electrically conductive paint. The finished keyboard is
then set aside to dry or cure, as the case may be, to form
the contact 2A.
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10378~5
Note that the drawings show 3 or 4 dimples 5 or 3 or 4
portions 4A but this is just for convenience in drawing and
illustrating the invention. The number of such dimples 5 and
portions 4A are not intended to be restricted to any certain ~ --
number but are intended to be limited by practicality and need.
As mentioned supra, the insulating rubber keyboard 4
is preformed and the process and article thereby are not intended
to be encompassed by this invention. The rubber keyboard can
be any resilient rubber material which has electrical insulating
properties. Preferred for this invention are curable silicone
rubbers. Silicone rubbers are well known in the art and are
well known to be electrically insulative. For those unfamiliar
with such silicone rubbers, attention is directed to U.S. Patents
Nos. 2,823,218; 3,159,601; 3,188,299 and 3,192,181. Also known
are silicone rubbers that cure by the action of peroxide catalysis
on unsaturated groups on silicon.
The electrically conductive paint can be a commercial
paint containing a resin, pigments, conductive particles and
~ solvents or the electrically conductive paint can be a rubber 20 dispersion in water or solvent, said dispersion also containing
pigments and/or conductive particles.
Preferred for this invention are silicone rubber
dispersions containing electrically conductive particles or
pigments. The amount of electrically conductive paint that is
layered on the flat fixbd plate 1 can vary according to the
desired end use of the finished product. For most uses, i
however, the layer of electrically conductive paint on the
surface of the fixed flat plate should be 1 to 2 mm. thick
- in its uncured state. Depending upon the dilution of the base
resin or rubber in the paint solution, this amount of
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~037875
electrically conductive paint gives a contact point, when dried,
of 0.5 to 2 mm. thick. Layers of electrically conductive paint
which give in excess of 10 mm. in thickness are usually not
practical for this invention. Furthermore, layers of ~ -
electrically conductive paint which give less than 0.05 mm.
in thickness are also usually not practical for this invention. .
As noted earlier, the pressure necessary for the
portion 4A to contact the wet electrically conductive paint is
provided by way of a roller. Roller means are common in the
art and no further elaboration is required. ;
While the invention has been particularly shown
and described with reference to specific embodiments, it is
to be understood by those skilled in the art that various
changes in form and detail may be made without departing from
the spirit and scope of the invention.
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