U.S. patent number 3,584,162 [Application Number 05/011,494] was granted by the patent office on 1971-06-08 for electrical keyboard switch mechanism with improved resilient diaphragm contact actuator.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Morris Krakinowski.
United States Patent |
3,584,162 |
Krakinowski |
June 8, 1971 |
ELECTRICAL KEYBOARD SWITCH MECHANISM WITH IMPROVED RESILIENT
DIAPHRAGM CONTACT ACTUATOR
Abstract
A keying mechanism is described which can be advantageously
employed in a high density or highly miniaturized keyboard. The
mechanism employs the principles of an elastic diaphragm switch
but, instead of including a continuous elastomeric sheet, such
switch comprises a discrete elastomeric plunger for each key
operating position, the plungers being freely guided through an
apertured guide plate. An elastomeric nomenclature sheet is
provided on the guide plate to provide key indicia and to seal the
mechanism against dust and dirt. A metallic grid having apertures
at the key positions is provided on the nomenclature sheet and
functions to prevent accidental triggering of the keyboard.
Inventors: |
Krakinowski; Morris (Ossining,
NY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
21750628 |
Appl.
No.: |
05/011,494 |
Filed: |
February 16, 1970 |
Current U.S.
Class: |
200/5A; 200/83N;
200/517; 341/28; 200/46; 200/86R; 235/145R; 400/479 |
Current CPC
Class: |
B41J
5/08 (20130101); H01H 13/702 (20130101); H01H
2239/026 (20130101); H01H 2219/028 (20130101); H01H
2209/006 (20130101); H01H 2217/026 (20130101); H01H
2217/016 (20130101); H01H 2223/034 (20130101); H01H
2237/006 (20130101); H01H 2225/006 (20130101) |
Current International
Class: |
H01H
13/70 (20060101); H01H 13/702 (20060101); H01h
009/26 (); H01h 043/08 (); H01h 003/02 () |
Field of
Search: |
;200/1,5,17,18,46,52,83.8,86,86.1,86.5,159B,61.43,172 ;179/9K
;235/145 ;178/17 |
References Cited
[Referenced By]
U.S. Patent Documents
|
|
|
3120583 |
February 1964 |
Cornell |
3120584 |
February 1964 |
Grunfelder et al. |
3290439 |
December 1966 |
Willcox et al. |
3382338 |
May 1968 |
Arseneault et al. |
|
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Scott; J. R.
Claims
What I claim is:
1. A keying mechanism for a high density keyboard comprising:
a base assembly having an array of first conductive contact means
thereon, each of said contact means being disposed to be in
registration with a key position of said keyboard;
a substantially incompressible insulating layer overlaying said
base assembly, said insulating layer having spaced apertures
therethrough which are respectively aligned with said first contact
means,
a diaphragm assembly overlaying said insulating layer, said
diaphragm assembly having an array of second conductive contact
means, said diaphragm being disposed whereby respective first and
second conductive contact means are in opposed relationship and
normally separated by gaps respectively formed by said
openings,
an apertured guide plate above and spaced from said diaphragm, the
apertures in said plate being substantially in registration with
the apertures in said insulating layer;
a plurality of plungers for respectively being received in the
apertures of said guide plate, each of said plungers comprising a
larger and wider upper portion which is freely receivable within a
guide plate aperture and a second narrower and lower portion
extending from the base of said upper portion, said second and
lower portion being substantially in registration with said first
and second contact means, at least said lower portion of said
plunger comprising an elastomeric material; and
an elastomeric nomenclature sheet on the upper surface of said
guide plate to seal said mechanism against dust and dirt and
adapted to receive force from a stylus thereagainst at a keying
position to cause a corresponding plunger to force said first and
second contact means at a keying position into electrical
contact.
2. A keying mechanism as defined in claim 1 and further including a
perforated metallic layer on said nomenclature layer, the
perforations in said metallic layer being located at said key
positions, said nomenclature layer having different key indicia at
each of said key positions which are visible through said
perforations in said metallic layer.
3. A keying mechanism as defined in claim 1 wherein the elastomeric
material of said plunger is an elastomer filled with a nonshedding
lubricant.
4. A keying mechanism as defined in claim 1 wherein there is
further provided an apertured retaining sheet to which said guide
plate is affixed, the apertures of said retaining sheet being in
registration with the apertures of said guide plate and having
respective diameters of sufficient magnitude to permit the free
passage therethrough of the lower and narrower portions of said
plungers.
5. A keying mechanism as defined in claim 1 wherein the thickness
of said guide plate is so chosen whereby there is a gap between
said plungers and said nomenclature sheet.
6. A keying mechanism as defined in claim 1 wherein the upper and
lower portions of said plungers are cylindrical and wherein the
diameters of said lower portions are about one-half the diameters
of said upper portions, respectively.
7. A keying mechanism as defined in claim 6 wherein the respective
combined lengths of said upper and lower portions of said plungers
are at least equal to the diameters of said upper portions.
8. A keying mechanism for a keyboard comprising:
a base assembly having an array of first conductive contact means
thereon, each of said contact means being disposed to be in
registration with a key position of said keyboard;
a substantially incompressible insulating layer overlaying said
base assembly, said insulating layer having spaced apertures
therethrough which are respectively aligned with said first contact
means,
a diaphragm assembly overlaying said insulating layer, said
diaphragm assembly having an array of second conductive contact
means, said diaphragm being disposed whereby respective first and
second conductive contact means are in opposed relationship and
normally separated by gaps respectively formed by said
openings,
an apertured guide plate above and spaced from said diaphragm, the
apertures in said plate being substantially in registration with
the apertures in said insulating layer;
a plurality of plungers for respectively being received in the
apertures of said guide plate and disposed in registration with
said first and second contact means, at least the lower portion of
a plunger comprising an elastomeric material; and
an elastomeric nomenclature sheet on the upper surface of said
guide plate to seal said mechanism against dust and dirt and
adapted to receive force from a stylus thereagainst at a keying
position to cause a corresponding plunger to force said first and
second contact means at a keying position into electrical
contact.
9. A keying mechanism as defined in claim 1 wherein the elastomeric
material of said plunger is an elastomer filled with a lubricant.
Description
BACKGROUND OF THE INVENTION
This invention relates to switch mechanisms. More particularly, it
relates to a switch mechanism advantageously suitable for use as a
keying structure for a high density or a miniaturized keyboard.
Keyboards which are used for input of Chinese, Japanese and other
East Asian languages, for example, require a great many keys. A
practical Japanese keyboard, for example, has to include from 2500
to 6000 keys if a unique character is assigned to each key
position. With this type of keyboard, the size of each key and the
spacing between keys directly affects the overall size of the
keyboard, the latter size being ultimately limited by the reach of
the arms of an operator. It is readily evident that an operable
large-scale keyboard has to comprise scaled-down keys and the
spacing between keys has to be substantially reduced as compared
with the spacing between keys on conventional keyboards.
Since in the East Asian languages, the characters are quite
visually complex, there also has to be taken into account the
legibility of these characters as marked on key surfaces. It has
been found that a practical compromise in a 3600 key keyboard
between the legibility (essentially character size and spacing
between keys) and overall size of the keyboard is one in which the
keys are 0.166 inch 12 points) square and are spaced about 0.069
inch from each other, i.e., the distance between corresponding
edges of adjacent keys is 0.235 inch (17 points). The miniaturized
keys are, in this type of structure, actuated with a hand-held
stylus or an "extension" attached to an operator's finger.
Relative to the facile operation of a high density highly
miniaturized keyboard, reference is made to U.S. Pat. No. 3,308,253
to Morris Krakinowski, dated Mar. 7, 1967, and assigned to the
assignee of this invention, wherein there is disclosed a novel
diaphragm switch. In the latter switch, there is employed an
elastomeric layer which is deformable in response to light pressure
to effect an electrical contact. This switch has been found to be
efficacious in requiring a light touch by a keyboard operator and
the principles underlying the construction of this switch lend
themselves advantageously to their employment in highly
miniaturized, high density keyboards.
However, in the construction of high density keyboards, using the
principle of the elastic diaphragm switch as disclosed in the
above-mentioned patent, it has been found that crosstalk occurs
between adjacent keys, i.e., wherein the actuation of a particular
key results in the closing both of the contacts for that key and
the contacts of an adjacent key. This is particularly
disadvantageous where multiple contacts may occur at a single
operating, i.e., key position.
It is, of course, appreciated that all of the factors which come
into play in the case of a practicable high-density keyboard also
obtain in a highly miniaturized keyboard with a conventional number
of keys.
Accordingly, it is an important object of this invention to provide
a miniaturized keying mechanism wherein the danger of crosstalk to
adjacent key positions is prevented.
It is another object to provide a keying mechanism in accordance
with the preceding object whose construction includes the
principles underlying the structure of an elastic diaphragm switch,
thereby rendering the operation of the keying mechanism physically
facile.
In the switching arrangement for the keyboard, there may be present
contact complexes, i.e., multiple contacts at an operating
position.
Therefore, it is a further object of the invention to provide a
miniaturized keying mechanism wherein despite the presence of
multiple contacts, i.e., contact sets at respective operating
positions, complete electrical isolation is maintained
therebetween.
SUMMARY OF THE INVENTION
Generally speaking and in accordance with the invention, there is
provided a keying mechanism for a high density keyboard. The
mechanism comprises a base assembly having an array of first
conductive contact means thereon, each of the contact means being
disposed to be in registration with a key position of the keyboard.
There is included a substantially incompressible insulating layer
overlaying the base assembly, the insulating layer having spaced
apertures therethrough which are respectively aligned with first
contact means. A diaphragm assembly is provided which overlays the
insulating layer, the diaphragm assembly having second conductive
contact means thereon and being disposed whereby the first and
second conductive contact means are in opposed relationship and
normally separated by gaps respectively formed by the
aforementioned apertures in the insulating layer. There is also
provided an apertured guide plate above and spaced from the
diaphragm, the apertures in the guide plate being substantially in
registration with the apertures in the insulating layer. A
plurality of plungers are provided for respectively being received
in the apertures of the guide plates, each of the plungers
comprising a larger and wider upper portion which is freely
receivable within a guide plate aperture and a second narrower and
lower portion which is substantially in registration with the first
and second conductive contact means. At least the aforesaid lower
portion of a plunger comprises an elastomeric material. There is
also included an elastomeric nomenclature sheet on the upper
surface of the guide plate to seal the mechanism against dust and
dirt. The nomenclature sheet is adapted to receive force from a
stylus thereagainst at a key position to cause a corresponding
plunger to force the first and second contact means at a keying
position into electrical contact. The nomenclature sheet also has
marked thereon, respective key indicia at each discrete key
position.
The foregoing and other objects, features and advantages of the
invention will be apparent from the following more particular
description of a preferred embodiment of the invention, as
illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, FIG. 1 is a plan view of a portion of an
illustrative embodiment of a keying mechanism constructed in
accordance with the principles of the invention;
FIG. 2 is a view, partly in section, taken along lines 2-2 of FIG.
1;
FIG. 3 is a view taken along lines 3-3 of FIG. 2; and
FIG. 4 is a vertical view, partly in section, of a single key
position as operated by a stylus.
DESCRIPTION OF A PREFERRED EMBODIMENT
Referring now to FIG. 1, there is shown therein a plan view of a
portion of a miniaturized keyboard whose dimensions are chosen to
be suitable for use for a language such as Japanese or Chinese, for
example. These languages may require a keyboard having from 2500 to
6000 character keys. Practicable dimensions for the keys and the
spacing therebetween in such keyboard may be a key side of 12
points (0.166 inch) and a distance between the corresponding sides
of adjacent keys of 17 points (0.235 inch), whereby the space
between adjacent keys is about 5 points (0.069 inch).
In FIG. 2, wherein there is shown an illustrative embodiment
constructed in accordance with the principles of the invention, the
portion at the base of the figure is essentially the elastic
diaphragm switch disclosed in U.S. Pat. No. 3,308,253 without the
elastomeric layer of the latter switch. Such switch includes a
substrate 10 having a plurality of segments of conductive material
12 and 12A provided on its upper surface, the latter plurality of
segments being employed to illustrate multiple contact complexes at
respective single key operating positions. These contacts may
comprise a grid such as described in Patent application of Hans Y.
Juliusberger, Morris Krakinowski and George R. Stilwell, Jr.
entitled, "Multiple Switch Encoding Device," , Ser. No. 791,406,
filed Jan. 15, 1969 and assigned to the IBM Corporation. Thus, the
contacts are always interconnected in some fashion. The
interconnections (signal lines), as shown in FIG. 3, form a
pattern, i.e., coding scheme. In this connection, it is
advantageous to perform some of the encoding in the keyboard.
Overlying substrate 10 is a layer of insulating material 14, the
insulating material being chosen to be incompressible and being
constructed to have openings in the areas of the conducting
segments 12 and 12A. Disposed on insulating material layer 14 is a
diaphragm 16 having conductive segments 20 and 20A on its
underside, conducting segments 20 and 20A having configurations
respectively to adapt them to be brought into electrical contact
with segments 12 and 12A. Here, of course, the comments relative to
keyboard encoding obtain. A salient difference between the
elastomeric switch shown in U.S. Pat. No. 3,308,253 and the keying
mechanism of this invention is the use of elastomeric plungers
rather than an elastomeric layer as is further described
hereinbelow.
Relative to the structures described so far, and as set forth in
the aforementioned patent, substrate 10 may be copper-clad glass or
paper-filled epoxy laminate and may be about 0.06 inch thick with
one oz. copper per square foot. Insulating layer 14 may be of Mylar
with a thickness of about 0.001 to 0.005 inch. Diaphragm 18 may be
of a Mylar-copper laminate with a thickness of 0.002 to 0.006 inch
with 1/2 to 1 oz. copper per square foot. Contacts 12, 12A and 20
and 20A are suitably chosen to be of gold and are 50 to 150 .times.
10.sup..sup.- inch thick.
The elastomeric plungers 22 for each key position respectively may
be right circular cylinders comprising a first and upper portion
22A suitably having diameter D and a height about equal to or a
little less than D and a second and lower portion 22B which may
suitable have a diameter of one-half D. A practical design example
is where L (the sum of the heights of first portion 22A and second
portion 22B) is approximately equal to D where D may be about
three-sixteenth inch. In a plunger 22, portions 22A and 22B may
suitably be integral with each other and may consist of an
elastomer such as neoprene and be relatively hard (60--80 Durometer
Shore A-scale). However, upper portion 22A need not be of an
elastomeric material. The plungers are freely guided in a guide
plate 24 which permits free vertical movement of the plungers
therein, guide plate 24 suitably comprising a rigid plastic molding
having good dimensional stability such as polycarbonate molding
resins. Guide plate 24 has attached to it a thin (0.005 to 0.010
inch thick) retainer 26 which may comprise Mylar. Retainer 26 is
affixed to plate 24 by a suitable adhesive and functions as a tray
in the assembling and disassembling of a keyboard.
It is realized, of course, that guide plate 24 has to have a number
of openings therethrough sufficient to freely receive all of the
plunger portions 22A and that retainer plate 26 has to be
perforated with a like number of apertures to freely accommodate
all of the plunger portions 22B. In this connection, diaphragm 18
is chosen to have a stiffness such as to fully mechanically support
plungers 22. The weight of a plunger 22 is chosen to be about 0.1
gram while the force required to operate a keying position is 20 to
30 grams.
Disposed on guide plate 24 is a nomenclature sheet 28 on whose
upper surface there are printed the key designations at the
corresponding key positions. Nomenclature sheet 28 is chosen to be
a thin sheet (0.015-- 0.020 inch) of an elastomeric material such
as a polyurethane elastomer. Sheet 28 functions, in addition to
providing key indicia, to seal the plunger-switch combination
against dust and dirt and to provide a further elastomeric element
in the operation of the keyboard. Disposed on nomenclature sheet 28
is a protective plate 30 which is perforated to expose the key
indicia on nomenclature sheet 28. Plate 30 is preferably chosen to
be a thin metallic sheet (about 0.015 inch thick) and functions to
maintain nomenclature sheet 28 in position and prevents the
accidental triggering of the keyboard in the event that an operator
inadvertently leans his arms thereon or in the event that the
mechanism is jarred for some other reason. It is noted that a
normal gap (about 0.005 to 0.010 inch) exists between the under
surface of nomenclature sheet 28 and the upper surface of plunger
22.
FIG. 3 is included to provide a view taken along lines 3-3 of FIG.
2. In this view, there are shown the disposition of contacts 12 and
12A on substrate 10 and contacts 20 and 20A on the underside of
diaphragm 18. The width spanning the breadth of contacts 20 and 20A
is chosen to be equal to or greater than the diameter of portion
22B of a plunger 22. In this figure, there can also be seen the
configuration and relative size of the apertures in insulating
layer 14. Preferably, the apertures are chosen to have a size such
that insulating sheet 14 rests on the conductive segments 12 and
12A. The aperture openings can also be circular.
In FIG. 4, there are seen the conditions which obtain when a key
position is operated. A rigid stylus 32 is passed through an
aperture in plate 30 to press down on elastomeric nomenclature
sheet 28 which deforms in response to the pressure to force down
plunger 22. Plunger 22 rides freely in its opening in guide plate
24 and plunger portion 22B presses down on diaphragm 18 to cause
opposing contacts 20 and 12, and 20A and 12A to make electrical
contact. When plunger portion 22B is forced down on against
diaphragm 18, its elastomeric character causes it to be deformed
and to spread outwardly at its base portion. In this situation,
therefore, the ratio of the diameter of portion 22B when it is
under stress conditions to its diameter when it is underformed (at
rest) is about equal to or more than one.
In considering the operation of this invention, it can be
understood that the respective plungers 22 perform the same
force-spreading function as the elastomeric sheet performs in the
switch disclosed in the above-mentioned U.S. Pat. No. 3,308,253.
Nomenclature sheet 28 in combination with the plunger 22 functions
as a protective bumper against overload. A plunger 22 distributes
the load over a relatively large area of the contacts 12, 12A and
20, 20A. As the external load increases, the area of contact
between diaphragm 18 and substrate 10 further increases thereby
decreasing contact resistance. The relatively thick elastomeric
plunger 22 which is approximately three-sixteenth inch in height
does not readily conform to the shape of rigid stylus 32 whereby no
localized stress is generated which can damage diaphragm 18. The
restoring force resulting from the deformation of diaphragm 18 in
the operation of a key position with a stylus has to overcome the
small amount of friction that exists between a freely guided
plunger 22 and guide plate 24. To reduce such friction, plunger 22
or at least portion 22B thereof can comprise neoprene filled with a
nonshedding lubricant such as a silicone, or the like can be
employed. In this connection, the elastomer constituting plunger 22
is preferably of the nonwater absorbing, nonswelling type.
It is seen that with the keying mechanism of this invention since
good contact can be made at a single position between multiple
contact sets without the danger of "crosstalk", the keyboard can
generate a unique code for each operating key position. The active
elastic diaphragm switch area is relatively large compared with
switch separation. For example, the elastic diaphragm switch
separator for the high density, light touch keyboard may have an
aperture 0.172 inch while the switch separation is only 0.235 inch.
The known elastic diaphragm switch shown in Pat. No. 3,308,253
employs a continuous elastomer sheet for the whole switch array.
Using such a switch, the stress wave in the elastomer due to
deformation in operation would trigger closely located, i.e., large
area switches. However, in this invention, the motion of a freely
guided plunger is completely isolated from adjacent key positions.
The plunger concentrates the keying force on the contacts of the
diaphragm whereby there results a highly localized deformation of
the diaphragm in the specific contact area, as is seen in FIG. 3.
With this arrangement, the problem of "crosstalk" between adjacent
key positions is prevented.
While the invention has been particularly shown and described with
reference to a preferred embodiment thereof, it will be understood
by those skilled in the art that various changes in form and
details may be made therein without departing from the spirit and
scope of the invention.
* * * * *