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Description  |
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BACKGROUND
The present invention relates generally to switches, specifically to
switches actuated by touch, and more specifically to membrane switch
apparatus.
An increasing demand for switch apparatus having the ability to provide
sequential output signals for use with electric circuits is now being
experienced. For example, in touch-tone telephone switches, electrical
connection must be made between a common conductor, one high tone contact,
and one low tone contact before the DC current of the electric circuit is
turned on.
Further increased interest in electronic apparatus having switch keyboards,
such as calculators, typewriters, and similar apparatus, has increased the
demand for keyboard apparatus. Such keyboard apparatus preferably includes
a minimum number of components which can be easily manufactured and which
lend themselves to mass production techniques, thus reducing the cost of
materials and labor.
SUMMARY
The apparatus of the present invention solves these and other problems in
membrane switch apparatus by providing, in the preferred embodiment,
membrane switch apparatus including at least first switch electrode
members and at least second electrode members electrically insulated from
the first electrode members. A flexible, nonconductive member is disposed
in a spaced relation above and adjacent to the level of the top surfaces
of the electrode members and includes conductive members formed thereon
allowing sequential electrical contact of the first electrode members and
the second electrode members.
It is a primary object of the present invention to provide novel membrane
switch apparatus.
It is a further object of the present invention to provide a membrane
switch apparatus which includes a minimum number of components.
It is a further object of the present invention to provide a membrane
switch apparatus which is simple in design, easy to manufacture, lends
itself to mass production techniques, and which maximises utilization of
the materials used.
It is a further object of the present invention to provide a membrane
switch apparatus which provides sequential output signals for use with the
electric circuits.
It is a further object of the present invention to provide a membrane
switch apparatus which can be utilized in keyboard apparatus.
These and other objects and advantages of the present invention will become
clearer in the light of the following detailed description of an
illustrative embodiment of this invention described in connection with the
drawings.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of membrane switch apparatus
according to the present invention;
FIG. 2 is a top view of the electrodes of the apparatus of FIG. 1;
FIG. 3 is a mirror image bottom view of a modified membrane member of the
apparatus of FIG. 1;
FIG. 4 is a cross-sectional view of the apparatus of FIG. 1, with
individual switching units shown as being actuated by fingers; and
FIG. 5 is a cross-sectional view of the apparatus according to FIGS. 1 and
3, with individual switching units shown as being actuated by fingers.
DESCRIPTION
In FIGS. 1, 2 and 4, a preferred form of membrane keyboard apparatus
utilizing the teachings of the present invention is generally designated
10. Keyboard 10 includes an insulator component 12, a member 14 for
positioning the membrane in a spaced relation above and adjacent to the
level of the top surfaces of the electrode members of the array of
individual switching units, and a membrane member 16. Insulator component
12 includes an insulator 18 having a first face 19. An array of individual
switching units 20-31, are located on and supported by face 19 of
insulator 18. Switching units 20-31 are arranged in three columns
designated 32, 34, and 36 and four rows designated 40, 42, 44, and 46.
Therefore, switching unit 20 is located in column 32 and row 40, and
switching unit 27 is located in column 34 and row 44, with the remaining
switching units being located at the various intersections of the columns
32, 34, and 36 with the rows 40, 42, 44, and 46.
Each of the individual switching units 20-31 include a plurality of first
electrode members, shown in the preferred embodiment as electrode members
a, b, and c. Electrode members a-c are electrically insulated from each
other and are located generally centrally of the switching units.
Electrode members a-c have a top surface 50, illustrated in FIGS. 4 and 5.
Therefore, switching unit 20 includes a plurality of first electrode
members identified as electrode members 20a, 20b, and 20c, and similar
designations are used for switching units 21-31.
Each of the individual switching units 20-31 include a plurality of second
electrode members, shown in the preferred embodiment as electrode members
d and e. Electrode members d and e are electrically insulated from each
other and from electrode members a-c. Electrode members d and e may be
located generally at the periphery of the switching units 20-31, on
opposite sides of electrode members a-c, and further removed from the
center of the switch actuation locus. Electrode members d and e have a top
surface generally designated 52 which, in the preferred embodiment, has a
height level equal to the height level of top surface 50 of electrode
members a-c. Therefore, switching unit 20 includes a plurality of second
electrode members identified as electrode members 20d and 20e, and similar
designations are used for switching units 21-31.
Insulator component 12 further includes a conductive sheet member 54 having
a top surface 64 and which is arranged in a patterned arrangement around
switching units 20-31. Generally, sheet member 54 includes portions 56-59
arranged adjacent the columns 32, 34, and 36 of the array of individual
switching units 20-31 and portions 60 and 61 arranged above row 40 and
below row 46, respectively, of the array of individual switching units
20-31. Portions 56-61 are electrically insulated from each other. In the
preferred embodiment, portions 57 and 58 have removed portions 66 passing
entirely therethrough between row 42 and 44 of the array of individual
switching units, whose purpose will be explained hereinafter.
As best illustrated FIG. 2 electrode members a-c are formed from linear
strips of conductive material and electrode members d and e formed of
truncated, semicircular members. Electrode members 20a, 23a, and 26a are
each electrically connected to separate, enlarged electrical connection
members 68 used for electrically connecting electrode members 20a, 23a,
and 26a to electric circuits, not specifically shown. Electrode member 29a
is electrically connected to electrical connection element 70 allowing
electrical connection to electric circuits, not specifically shown.
Electrode members 20b, 23b, 26b, and 29b are formed from and electrically
connected together by a continuous linear strip 72 electrically connected
to an electrical connection element 90 allowing electrical connection to
electric circuits, not specifically shown. Similarly, electrode members
20c, 23c, 26c, and 29c are formed from and electrically connected together
by a continuous linear strip 74 electrically connected to an electrical
connection member 94 allowing electrical connection to electrical
circuits, not specifically shown.
Electrode members 20d, 23d, 26d, and 29d are electrically connected
together by arcuate strips 76 located therebetween. Included in at least
one of arcuate strips 76 is an electrical connection member 96 also used
for electrically connecting electrode members 20d, 23d, 26d, and 29d to
electric circuits, not specifically shown. Electrode members 20e, 23e, 26e
and 29e are electrically connected together by linear strips 78 located
therebetween. Electrical connection member 98 is further provided within
the removed portion 66 of portion 57 and electrically connected to at
least one strip 78 for electrically connecting electrode members 20e, 23e,
26e, and 29e to electric circuits, not specifically shown.
A complete and detailed description of electrode members a, b, c, d, and e
of switch units 20, 23, 26, and 29 located within column 32 of the array
of individual switch units 20-31 has now been set forth, and it can now be
appreciated that the electrode members a, b, c, d, and e, of switch units
21, 24, 27, and 30 located within column 34 and of switch units 22, 25,
28, and 31 located within column 36 are similarly arranged on face 20 of
insulator 18, except, in the preferred embodiment, that electrode members
a, b, c, d, and e of switch units 22, 25, 28, and 31 of column 36 are
arranged in a reverse mirror image.
It should further be noted, electrodes 21e, 24e, 27e, and 30e of column 34
and electrodes 22e, 25e, 28e, and 31e of column 36 may share a common
electrical connection member 98 located within removed portion 66 of
portion 58. Further, electrode 31a is electrically connected to an
electrical connection member 100. In the preferred embodiment, best
illustrated in FIG. 1, elements 90 of strips 72 forming electrode members
b of switch units 20-31 electrically contact and electrically connect with
portion 60, and electrical connection is made between portion 60 and the
electric circuits, not specifically shown. Similarly, elements 70 of
electrode members 20a, 30a, and 31a electrically contact and electrically
connect with portion 61.
It should be noted that the electrode means a, b, c, d, and e, strips 72,
74, 76, and 78, electrical connection members 68, 70, 90, 94, 96, 98, and
100, and portions 56-62 can be formed by any suitable method such as by
printing on an insulator or etching a conductive clad insulator, or
similar techniques may be used.
Membrane member 16 is formed of a thin, flexible, sheet member 80 having a
high strength to mass ratio and including a bottom surface 82. Sheet
member 80 is preferably formed of nonconductive material, such as
polyester sold under the trade name Mylar having a thickness substantially
equal to between 3 to 10 mils (0.00772 to 0.0254 centimeters). Membrane
member 16 further includes an array of conductive members corresponding to
the array of individual switch units 20-31 formed on bottom surface 82 of
sheet member 80.
Each conductive member includes a first conductive portion generally shown
and designated f, generally located adjacent to the center of switch
actuation locus and generally vertically above and adjacent to electrode
members a, b, and c for electrically contacting and bridging between first
switch electrode members a, b, and c. Each conductive member further
includes a second conductive portion electrically insulated from first
conductive portion f, shown in the preferred embodiment as conductive
portions g and h. Conductive portion g is arranged generally vertically
above and adjacent to electrode member d for electrically contacting
therewith and conductive portion h is arranged generally vertically above
and adjacent to electrode member e for electrically contacting therewith.
Second conductive portion, as shown in the preferred embodiment as
portions g and h, is located generally at the periphery of the switch
actuation locus and further removed from the center of the switch
actuation locus. Conductive portions g and h are electrically connected to
each other by conductive material 84. Therefore, when conductive portion g
electrically contacts electrode member d and conductive portion h
electrically contacts electrode member e, conductive portions g and h and
material 84 electrically bridge between electrode members d and e. Portion
g of switch units 20, 23, 26, and 29 of column 32 may be electically
connected together and formed by continuous conductive patterns 86.
Portions h of switch units 20, 23, 26, and 29 of column 32 may be
electrically connected together and formed by continuous conductive
patterns 88. Conductive portions g and h of switch units 21, 22, 24, 25,
27, 28, 30, and 31 of columns 34 and 36 of the array of individual switch
units may be formed in a similar manner. Therefore portions g and h and
material 84 form a ladder type arrangements where patterns 86 and 88 form
the runners and material 84 forms the rungs or steps. Material 84 and
conductive patterns 86 and 88 may be formed from a resistive or
carbonacous paint or silver or other conductive material sprayed or
screened on bottom surface 82 of sheet member 80 and having a thickness of
substantially 0.1 mils (0.000254 centimeters).
It will be appreciated that individual switching unit 20 includes first
conductive portion 20f which electrically contacts and bridges between
first electrode members 20a, 20b, and 20c and second conductive portions
20g and 20h which electrically contacts second electrode members 20d and
20e, respectively, and due to material 84, electrically bridges
therebetween. The remaining switch units 21-31 are similarly constructed.
Keyboard 10 further includes a spacer 14 for positioning membrane member 16
in a spaced relation above and adjacent to the level of the top surface of
the electrode members a-c of individual switching units 10-31. Spacer 14
is formed of non-conductive material such as Mylar plastic film and
includes an array of apertures 102 formed therethrough corresponding to
the array of individual switching units 20-31. Therefore, apertures 102
are located over and expose electrode members a, b, c, d, and e of the
individual switching units 20-31. As best seen in FIG. 4, spacer 14 rests
on insulator component 12 and supports membrane member 16. Therefore,
portions f-h formed on sheet member 80 of membrane member 16 are held in a
spaced relation above and adjacent to electrode members a-e of individual
switch units 20-31. It should be noted that portions 56-61 may be omitted
if insulator 14 of the first preferred embodiment is provided.
An alternate preferred form of the means for positioning membrane member 16
in a spaced relation above and adjacent to the level of the top surfaces
of the electrode members a-c of individual switch units 20--31 is shown in
FIGS. 3 and 5. As shown in FIG. 3, membrane member 16 further includes
insulator members 104 formed of nonconductive material which is placed on
bottom surface 82 of sheet member 80 over material 84 and strips 86 and 88
located adjacent thereto, whose purpose will be explained hereinafter.
In the second embodiment, top surface 64 of portions 56-61 is spaced
vertically above top surfaces 50 and 52 of electrode members a, b, and c
and d and e, respectively. In other words, the coplanar top surface 64 of
portions 56-61 lie above the coplanar top surfaces 50 and 52 of electrode
members a-e forming the plurality of first and second electrode members of
individual switching units 20-31. Therefore, membrane member 16 can rest
directly on and be supported by top surface 64 of portions 56-61, as seen
in FIG. 5. Therefore, portions f-h formed on sheet member 80 of membrane
member 16 are held in a spaced relation above and adjacent to electrode
members a-e of individual switch units 20-31.
The insulator members 104 formed on membrane member 16 prevent accidental
bridging of strips 72 and 74 by conductive material 84 between rows 40,
42, 44, and 46 of the array of individual switching units 20-31. For
example, if pressure was placed on membrane member 16 at an area above
conductive material 84 out of the switch actuation locus rather than the
area above conductive portions f, g, and h within the switch actuation
locus, insulator members 104 prevent conductive material 84 located
between strip 86 and 88 from bridging between strips 72 and 74 or with
electrical connection members 68.
It will be appreciated that although electrode members a-e and their
associated electrical connection means and portions f-h are shown in their
preferred form, other forms of electrode members a-e, electrical
connection means and portions f-h will be known to those skilled in the
art upon reading and understanding of the present invention. For example,
electrode members a-e and portions f-h can be formed such that insulator
members 104 will not be required as shown in the second preferred
embodiment.
OPERATION
Generally, in operating the membrane keyboard apparatus 10 according to the
teachings of the present invention, the finger of an operator is placed
upon a selected individual switch unit, of units 20-31, for example,
switch unit 29 and finger 92 and switch unit 30 and finger 93 as shown in
FIGS. 4 and 5.
In an unactuated position, portions f, g, and h are held in a spaced
relation above and adjacent to electrode members a, b, c, d, and e by
insulator member 14 as shown in FIGS. 1, 2, and 4 or by portions 56-61 as
shown in FIGS. 3 and 5.
Upon placement of finger 92 or 93 on a selected individual switching unit,
of units 20-31, for example, switching units 20 or 30 as shown in FIGS. 4
and 5, pressure would then be placed on membrane member 16 by the finger.
Membrane member 16 would then deflect in the direction of the pressure
applied by the finger, or in other words, in a concave fashion. Since
portions f, g, and h are located on bottom surface 82 of sheet member 80
forming membrane member 16, portions f, g, and h will deflect towards
electrodes a-e. As sheet member 80 deflects, portion f will initially
deflect at a greater rate in that portion f is located generally centrally
of the switch actuation locus. In the preferred embodiment, portion f lies
generally centrally of the concave deflection of sheet member 80 by the
finger. Therefore, portion f will electrically contact and bridge between
electrode members a, b, and c before portion g and h electrically contact
electrode members d and e, respectively, as best seen in FIGS. 4 and 5 by
finger 92 deflecting portion 30f into electrode members 30a, 30b, and 30c
of individual switching unit 30. Upon continued deflection of sheet member
80 by the finger, member 80 will continue to deflect until portions g and
h, located at the periphery of the switch actuation locus and further
removed from the center of the switch actuation locus, electrically
contact and bridge between electrode members d and e, respectively, as
best seen in FIGS. 4 and 5 by finger 93 deflecting portions 29f into
electrode members 20a, 20b, 29c and portions 29g and 29h into electrode
members 29d and 29e, respectively, of switching unit 29.
Therefore, a sequential output signal is made to the electric circuits in
that a first output signal is received by the electric circuits by the
electrical connection and bridging of switch electrode members a, b, and c
by portion f and a second output signal is received by the electric
circuits by the electrical connection and bridging of electrode members d
and e by portions g and h. It should be noted, that it is impossible for
portions g and h to electrically contact and bridge between switch
electrode members d and e before portion f electrically contacts and
bridges between switch electrodes a, b, and c. This can be used, for
example, to create a mechanical interlock assuring that electrical contact
is made with first electrode members before electrical contact is made
with second electrode members, such as in touch-tone telephonic
switchboards.
When the operator removes finger 92 or 93 from membrane member 16, member
16 will return to its first, nonactuated position. Individual switch unit
29 or 30 is thus returned to an open switch position because portions f-h
are electrically spaced and insulated from electrode members a-e.
A further sublety of the switch elements of the switch apparatus of the
present invention can now be appreciated. In the preferred embodiment,
switch electrodes a, b, and c are located generally centrally of the
switch actuation locus and electrodes d and e are located on opposite
sides of electrode members a, b, and c and generally at the periphery of
the switch actuation locus and further removed from the center of the
switch actuation locus. Electrical connection is made by portions g and h
and material 84 and therefore create a U-shaped electrical connection
bridging path between electrode members d and e. Therefore, if sheet
member forming membrane member 16 were to be deflected by a sharp object
other than a rounded object such as the finger of the operator, for
example, in an extreme case, by the use of a ball-point pen such that
membrane member 16 does not deflect in a concave fashion or deflect
generally centrally from the switch actuation locus, and therefore portion
g electrically contacts electrical member d or portion h electrically
contacts electrode member e before electrical connection is made between
portion f and all of electrode members a, b, c, electrical connection
between electrode members d and e will not be made in that in order to
deflect member 80 into both electrodes d and e simultaneously, it would
require that member 80 also deflect into electrode members a, b, and c
before electrical connection is made between electrode members d and e due
to the preferred structure of the preferred embodiment.
The membrane keyboard apparatus 10 according to the present invention lends
itself to mass production techniques. For example, to assemble apparatus
10, membrane member 16, insulator 14, and insulator component 12 are
simply dropped into a bezel member, not shown, in the first preferred
embodiment, or membrane member 16 and insulator component 12 are simply
dropped into a bezel member, not shown, in the second preferred
embodiment. It can further be appreciated that membrane keyboard apparatus
10 of the present invention includes only a minimum number of components
which can be easily manufactured at a low cost and which lend themselves
to mass production techniques, thus reducing the expenses for material and
labor.
While two embodiments of the invention have been described, the scope of
the invention is not to be limited thereby but is to be taken solely from
an interpretation of the claims which follow:
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