Note: Descriptions are shown in the official language in which they were submitted.
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PROXIMITY CONTROL SWITCHING PANELS
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This invention relates to a proxim~ty control
swltching panel including a plurality of capacitors each
comprising a command slectrode plate and at least one slave
electrod~ plata Qrranged in capac~tive relation.
In one form, a switch on a panel of the typa
referred to comprises a diel~ctric sheet having on one
race a command eleckrode plate and on its other face a
slave electrode plate in register w~th the command elec-
trode and connected to a switching circuitO In use the
0 81~ electrode plate 1~ charged so that wh0n the com~and
electrode plate is touched or clo~ely approached by a
; flnger for example, the slaYe electrode plate emit~ a
control si~nal to the swltching circuit. In othe~ arrange~
ments, such a swltch has two slave electrode plates o~
; 15 which ~ne is chargeable and the other is arra~ged to emit
.a control signal to tha swltching circuit.
Control panels bearlng such switche3 are being
used for an increasingly large ~umber of purposes~ The
~olloving are gi~a~ mer~ly as ~ample~s calculator, type-
writer and ~elephone koyboard~; dome~t~c cooker~ televlslon
alid sound reproduction apparatu3 controls; display panel
readout controls; elevator control~
It wlll bs apparent $hat these different co~-
trol panels r0q~re dlfferent labelled arrangement~ ef the
25 switch or ~witclhes which thay containO It will al~o be
apparent th.-,~t f'or ssries mas:3 production it :Is de~irable
*o standardise the typ~3 of eontrol panel produced to as
great an extent as i~ eompatible w~th customer r~quirements
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, and this ic the principal ob~ect o~ the pre~ent in~ention~
, Accordlng to the present i~ven-tion ther~ is
. pro~ided a pro~imity co~trol ~witchlng panel includlng a
plurality of capacitors each Gomprislng a comma~d electrode
,. 5 ,plate and at least one sla~e electrode plate arranged in
capaçitive relation~ characterised in that ~ald panel ln~
cludes a plurality of said capacitors and said command and
, said slave electrode plate~ are ligllt~transmittlng plates
, depo~ited on opposite sides of a lig~t-transmitti~g di01ectric
shest,and ln that behlnd said sheet there is a dislsctric
indexing sheet which ~s printed to exhibit a plurallty of
switch-identifying indicia, a said indicium being located
in register wlth each of at least some of said capacitor~.
~len making switching panels in accordance wlth
the inYention, it is posslble to achieve a very high degrea
of standardisation in manufa~ture. It i8 possible to
select a pattern for the array of switchlng capacitor3
so that switching panels for use with different ,circuitry
can all be made identical a3 regards their electrode plates
and the transparent dielectric sheet3 on which th~y are
deposited, and di~f~rent indexlng sheets can be incorpora~
ted in the panels accDrding to customer requlrementsO
Thus for examplc, ~witching capac~tors may be
arranged in a four-square matr~x. L~ such a switching
panel is to be incorpora~ted ln a telephone for 'Itouch dia
ling"~ an appropriatc lndexing sheet could be printed witl
indicia representing the ten digits to regi~ter with ten
of the switching capacitors~ and the telephone manufacturer
would connect the ten lndexed capacitors to approprlate
~0 . switching circ~itry~ On the other hand9 a switch~ng
panel incorporating an identical array of switching capaci
tors coul~ be incorp~rated in a calculator~ In that ca~e,
the calaulator manufacturer might require the indexing -
~heet to be pr~nted with indicla representing th~ ten digit~9
the dccimal point~ and the add, ~ubtract, multip~y, dl~lde,
. a~d ~qual~ functions~ Thus tha only change in the panel
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manufacturing proce~s whlch is required when making paneJs
for these different purpose~ is substitution of the indexing
sheet. This i5 a ~ery simple operationO
By propar selection ~ the patter~ of the array
5 of switching capacitor~l it is possible, from a 3tandardised
production, to obtain switching panels bearlng ~ractions or
multlples of the n~mber.o~ capacitors depo3ited ln a standard
arrayO T~lls may be done by dividing the standard array or
by ~uxtaposlng two or more such array~ as the.case may be. . lO In each caYe it i~ again aasy to adapt the~indexing sheet~
to customer requirements.
A further advantage of ~si~g indexing sheets
which are.separate from the capacito~ bearing sheets iq
. that deposition of the indicla does not interfare with the
15 process used to deposlt the olectrode plate~. ;
In pre~orred emb~diments of the invention, at
least some of said capacitorq comprise two slave electrode
plate~, namely a chargeable slave electrode plate and a
. discharging slave electrode plate, sincs this simplifies
20 the required switching clrcultry.
According to a ~econd aspeot of the invention~
there is pro~ided a proximity control switching panel in-
cluding a plurality of capacitors each comprising a command
electrode plate and at least one slave elsetrode plate
arranged in.capaciti~e relatlon, characterised in that 5a.
panel includes a plurality of said capacitor~ of whlch the
com~and and slave electrode plates are respecti~ely d~
posited on ~ro~t a~d rear dielectrlc ~hcets~ at least the
front-sheet and the command electrodes being light-trans
30 mittlng, and in that between ~aid front and rear sheots
there i~ sandwiched a die~ectric indexing ~heet ~hich sarr.~.;.
a plurality of switch~ldentifylng lndicia~ a said incicium
being located in regi~ter with each of at least ~me of said
capacltors.
In addition to the advantage~ reclted.herein-
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be~ore ~n respect o~ the flrst aspect of the lnvention~ a
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panel accordlng to the ~econd aspect of tha invention has
the further advantage of bei~g ea3ier to manu~actur~9 because
the-electrode plates may be depo~ited on a single surface
o~ly of their respective she~tO
In embodlments of the ~n~ention ~n it~ second
a~pect, said indicia may be appli~d to thQ indexing sheet
in any convenient manner9 but it i~ preferred that sald I
lndex~g sheet i~ pr~nted to exhibit said lndicla.
Deposition of the command electrode plates
of a panèl according to the second aspect of the invention 1
; simplified ~hen they are deposited on a single surface o~
a sheet as is preferred.
In some embodiments of either aspect of the
invention, 0ach ~a~d capacitor includes a Yingle ~lave plate
S for connection to switching circuitry, but a~ with the first
aspect, 30 with the second, i~ preferred embodiments, each
of at least some of said capacitor5 comprises two slave
electrode plates~ namsly a char~eable slave electrode plate
- and a discharging slave electrode plateO
I~ embodiments of the ~econd aspact of the inven~
tlon9 all said chargeable ~lave electrode plates are prefer-
ably deposited o~ a ~ingle surface of a sheet~ Likewise
all said discharging slave electrode plates are preferably
deposited on a single surface of a sheet.
In some proforred embodiments of th0 seco~d
aspect of the invention; ~aid chargeable ~lave electrode
plates a~d sald discharging slave electrode plates are
deposited on at l~a~ two d~fferent sh~et surfaces~ Such
~urfaces may ~e opposite ~urfaces of R single sheet or
surface3 of t~o or mor~ differe~t ~he0t~ ~hi~ facllitates
the arra~gement of conductors connected to the alectrode
plates~
~n other preferred embodiments of the second
aspect o~ the inventiDn9 all said slave electrode plate~
~re depo~ited on a slngle ~urface of a ~heet~ Thi~ ha~
the advantag~ that all thos~ electrod0 plate~ can be formed
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at ~ne anA tha same time.
Again ln embodiments o~ the sQcond aspact of
th~ inv0ntion lt i~ preferred that all electrode plates
and all sheets on which they are deposited are llght-
- 5 transmitting. This makes the electrode-bearing sheet~
~itable for incorporating in a switching panel together
with an indexing sheet haYing at lea~t one llght-trans-
mitting portion in reglster wlth a 3aid capacitGr ~o as
to enable ~ lndication of operatlon of ~ch s~itching
capacitor to be given by a light which may be located
behind th~ panel D ' ' '
In some preferred embodiments of either aspect
o~ the present invention~ said i~dexin~ sheet has at least
one light-transmitt~ng portion in register with a ~aid
capacitor.
As an alternativ~l or in addition~ sald indexing
~heet proferably includes a llght-transmltting display
section, This is especially valuable ~n th~ case~ of
for example calculators and telephone keyboard~ associated
with an encoded memory ba~c. In such cases a display
devlce may be located behind the panel to display the
progress of a calcula~ion or a talephone number recalled
from memory a~ the ca~e may be4
Advantageously9 th~ or at lea~t one said
electrode-bearing sh~et is of glass.
The indexing sheet is preferably of l~Lasil~
material~ for example R polyester such aspolyethylene
terephthalate, 5aid inde~ing sheet is preferably
between 50,',~ m and 120~ m in thick~e3s~ This range
meets requirement~ ~or the usual printlng technlqucs, and
reliabl~ operation of the capacitor switches i~ not
hindered in ~a~es whe~e the inde~ing sheet is loc~ted
between electrode-bearing sheetsv
Each of $he electrode plates i3 preferably
formed by ~ deposit of SnO2 or In203 which i~ optionally
doped to e~hance its conductivity. Such deposlts can
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be hard and abra~ion.r~si~tant while bein~ substantially
transparent.
- . In order to prev.ent spuriou3 wit,ching~ it is
- advantagoous to provide a shieldlng ~ectrode behind the
S electrode plates.
. In .~ome preferred embodiments of the inventi.on9
the sheets of the panel:are laminated togetherO This
can be dono v~ry conveniently by using doubl~ faced adheslve
film. Alternatively or in addition~. one ~heet of the
panel may be larger than the others which are assembled
thereto to l~ave a rebate which acco~modates a bead of
adhesive material bonding the pan~l sheets together.
PrefQrred embodiments of the lnY~ntion w~ll
. now be further described by way of example with ref~rence
to the accompanying drawings in which .
Figures 1 and 2 ~re cross sectional vie~
throu~h t;wo embodiments of the ln~ention9
Figure 3 is a plan v~ew of an insulating
substrate carrying chargeable and discharging electrodes9
Figure l~ 19 a plan view of an indexing
ubstr~te which could be used with a ~wl~chlng panel
incorporating the sub~tra~e of Figure 3, and
Figure~ 5 and 6 are partial ~ectional vi~ws
of a thlrd and a fourth embodiment of the inve~tion.
In ~i~ure 1, ~ glass sheet 1 has an optional
tin ox~de coatlng Z applied to the whol.e of on0 ~ace
thereof to serve as a.screening electrode and on its other
face it carr~es two pairs of ~lave electrode plates9 each
pair consisting of a chargeable electrod~.3 and a dis-
charging electrode 4. Thes~ electrod~s are also of t-ln
oxide, doped as necessary. Th0 discharging electrodes
4 are individllally connected by co~d~ctors 5 (which may
also be o~ tin oxide) to terminals 6 each of whlch iq
. ~ormed by a body o~ enamel applied to an end pOrtiDn of
the respectiva conducto~ 5O The terminal~ 6 are loc~ted
at ~ido margins of the pancl for connection to a~ociatad
clrcuitryO Th~ chargeable ~lectrod~s 3 ar~ conn~ct0d to
a common pot~ntial sourc~ (not shown)~
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Th~ ~ac~ of the substrate which b~ars the
1ave electrodes 39 4 may optionally be coverad by a thin
~transparent pla~tic film, ~or example npplied by 3praying
to prevent al~y conden3ation on that face from adversely
.affecting operation o~ the switche~0 ..
. ~lgure 3 illustrates an arrangement in which
.~ a ~i~taen switch panel ha3 a 3ingle terminal 7 ~or con-
nection to the potential source4 Sixteen charg~able
el~ctrode3 3 are connected to their common tsrminal 7
and their sixteen associated discharging e~eotrode~ 4
are connected ~ia conductors 5 to individual terminals 6
- for the connectlon of operating circuitry.
The po~ltion~ of some command electrodeY 11
are indicated in dotted lines.
.In ~igure 19 Rn indexing sheet 8 o~ dielect,ric
material~ for example a plastics such as polyethylene
terephthalate iY laid over the first electrod~-bearing
sheet 1 and has areas bearing indicia 9 located .in reglY.ter
with the electrode plates 3, 4. T~e indexing sheet 8
is of ~maller size than the first electrode-bearing ~heet
1 to leave a rebate around its periphery. A second
glass ~heet 10 which is transparent and of the qame size
as the ~ndexlng sheet 8 i~ laid o~er that sheet sc that
transparent command eloctrode plate depo~it~ for
example of doped tin oxlde~ are locatad in register w:Ll;
the indicia and char~eabl~ and discharging e.lectrodes
3, 4 to form capacltors 12~ 13. The rebate form~d by the
mar~in of the fir~t sheet 1 and t~e edge~ of the indexiI~g
ahset 8 and seco~d electrode~bearing ~heet 10 contains a
bead 14 of adhesi~e material to hold the sheet~ of the
panel together.
In operativn of the ~witch pan~ Llustra*~d
in ~igure 1, the chargeable Ylave electrods~ 3 are con~
nected *o a pulse generator while the dischar~lng slaYe
3~ electrodes 4 are individually ~onnec:tsd to a detector
ciI-cult. If a command plate 11 i~ touched9 or in some
cases even approached closely~ for example by a flnger~
the capac:ltance between the three electrode plal;es w~ll
be modi~l2di. Thls wîll accordingly mod~ fy ~he pul~3e
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signal dellvered by the discharging ~lave al~ctrode plate
. 49 a~d this modificatlon is detected to give a signal
. :which can be ampl~fied as necessary to control a switchlng
.. circuit to perform a desired ~unctlon. In caseq in
which it is not actually necessary to touch the electrodes
li, the sheet lO o~ which they are deposited may if
- de~ire~ be reversed so that the electrodes 11 ~re beneath
the surface of the panel.
In order to deposit a plurality of SnO2
electrodes on a dialectric she~t in a predatermined
. pattern in the formation of a capacitive touch control
swl~ch panell the following proce~s may be-adopted. A
.silk-screen stencil i8 prepared, and a negative masking
pattern of Wiederhold9 8 WIEDOPRINT AL (Trade Mark) ink i8
pr~nted on one slde of a.~itreous or ceram~c sheet. The
~heet is then con~eyed thro~h a heating ~tation, in whlch
the masking ink is b~ced to leave a dry po~dery adhor0nt
. masking residue9 and thence to a coating station where
it is sprayed with a solution of SnCl4 in known manner~
~hen the SnC14 solution contacts the heated shoets it is
pyroli~ed to giva a uniform overall coating o~ SnO2 80 nm
thick. After coolln~, the masking residue and o~erlying
regions of SnO2 are removed by brushing to leave a positive
; pa~rned SnO2 coating on one slde of the she~t. The
proce~ is then repeated using another silk-screen st;en~il
to provide a positive patterned SnO2 coatin~ on the other
side of the same sheat or on a di~ferent sheet as requirad
.to form the required array of capacitors.
In a modlfied process, both sides of a sheet
ara mas~ed and the ~heet i8 then b~ed, and SnO2 coatings
arc formed on both side~ of the ~heet i~ a ~ingle st.age
of the process by a high frequency c~thode sputtering
technique~
- Figur0 2 shows a s~milar panel whlch has been
. assembled in a ~lightly different way~ The only differ
enoe of substanca i~ th~t the adhe~l~e boad 14 of Pi~ure :l.
has b~en dispensed wlth9 and the ~dexing sheet 8 and
9 ~ i3
second electrode-bearlng sheet 10 are laminated to each
other and to the flrst electrode-bearlng sheet 1. This
is done by using double sided adhesive films L5 available
under the trade mark MACBOND.
A panel according to Figure 1 and havlng an
array of capacitor ~wltches as illustrated in Figure 3
- may be used in a calculator in which ~he various switches
would be arranged to enter numbars in a display, carry
out one or more of the four major arithmetical operations
and give an answer. All the sixteen switch capacitor~
can be used to thls e~fect. The sheet 1 will be larger
than illustrated in Figure 3 to provide a place for a display.
The d~play can be mounted upon the sheet l by any Icnown
means.
Figrure 4 illustrate~ an indexing ~heet suitable
~or use in a panel for such ~ calculator.
The substrate 8 is made of a film of clear
plastics material such as a polyester~ This film bears
indicia 9 ~hich may be made of different colours or colour
shades. The remaining space between the indicia 9 and
around a section 17 marked "display" is co~rered by an opacl-
fying coat~ng. The indicia and thc opacif3ring coating
are applied to the polyeclter film by a prlnting technique
such as off-set prlnting. The pl~tics film 8 may for
example by 50,~ m to 120`~ m in thickness.
The display section 17 remains transparent~
In the calculator, this sectlon is to be located ~n registar
- with a display device ~not shown) whlle khe indicia 9
will be in reg~ster with the switching capacitor3 as abov~
described. Furthermore, a small portion 16 of the in-
dexlng sheet 8 which is to be located in register with a
- switching capacitor may be left transparent if desired ~o
that a- signal light can be flashed on to ind~cate that
any key has been touchad. In the ~dexing sheet illustrated,
only those areas of the indexing sheet 8 whlch are to regist~r
with a switching capacitor which go~erns a function which
will rlot lmmediately ~odify the display~ that i9 to say
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the declmal point~ div~de, multiply, 3ubtract and add
~unctio~s, are provided with ~uch a transparent portlo~
16~ The use o~ slgnal lights in con~unction with suitable
circuitry for capacitive switchas as~ocia-ted with tho~e
indici~ can thu~ provlda a positive indicat$on that the
deslred Eunction ha~ in fact been keyed in. Such a
posltlve indication in resp~ct of the other ~wltches
w~11 normally be pro~lded by an immediate modification
~f the di~play in response to swltching,
A p~nel as described with re~erence to
Figur~s 1 and 3 may also be usad a~ a tel~phone keybcard.
Fer thls purpose9 only ten of the 3ixteen swltching
capacitors will be connected to the external circuitry
and indexed. Use can be made of an inde~lng sheet a~
illu~trated in Fl~ure 4 but wherei~ only the indicia
corre~ponding to the digits 1 to 9 and 0 appear. These
indlcla ~ill be placed in register with the selected
~witch capacitors. The area around the indlcia 9 corres
ponding to the sald ten digit~ is opacifled as de~cribed
above. The remaining ~ets of electrodes are not co~-
nected in circult, 80 that they do not form active ~witches,
A~ the electrode plate~ are made o* a transparent coat~ng
the non~selected switch capacitor3 will in practice be
invisible to the user as they are not ~doxed. Of course
if it is desired to provide some addltional facility
~uch as entering into or readlng from a coded m~mory
bank of frequently used telephone number~ or to provide
for recalling an oparator or for switching to an ex~ension
then the appropriate number of sets of electrodoq can
be connected to the desired circ~itry and appropriata
l~dicia provided.
In such a var$ant, the display panel 17
would ~o~e$ime3 b0 omitted~ and if that were done it woulrl
be preferable to proYide a light-transmitting portion
such as 16 ln register wlth each selected switch~ng
capacltor~
From a compar~son of those two ~xamples of
use it will be apparent that the same array of el~ctr~de~
has'bee~ used for the manufacture of the panel~. A
standardissd process may be used for depositlng'the elec-
' S trode plates on their substrates. This is of partlcularinterest when a coating is deposited by pyrolysis ~f
~etal compound on a hot sub~trate such as heated gla~s.
The control of the proces~ is slmplifi~d. Only the index~
ing sheet has to be substltuted-ln the panel. As those
inde~ing sheets are obtained by a printing technique it
i3 quite easy to modify the indicia as to their location,
' '- colour~ pattern, etc.~ without those modifications af~ec-
ting the more complicated proc~s~ ~tsed for depositing the
' eleGtrodes as would be the ¢ase i~ the indicia'were to
b0 applied to on~ of the sheets bearlng the electrodesO
Figure 5 illust~ates a further modification
o~ the embodiments shown in ~igures 1 and 2 in ~hich
similar elements are again given similar reference numerals.
The principal difference between the embodiments o~ Fl~tres
2'0 1 and 5 is that in Figur~ 5~ 'the chargeable ~lave alectrodes
3 are deposl'ted on a surface of a sheet lA which i9 di~erent
'- from the surface on whlch the discharging slave electrodes
4 ~re deposlted. In Figure 59 the sheet lA is a sh~et of
glass lntermediate in size, and located b~t~een the sheet
1 on which the discharg~g slavc electrodes 4 are de~o~ited
and the indexing ~heet 8v The chargeable slave electrodes
3 are connected to a common terminal 7.
The sheet~ of the switch panel of ~igure 5 may
be bonded together by a boad of adhe3ive analogous to that
sho~n at 14 in Figurc 1 and/or by usi~g three sheets of
double fac~d adhesive ~iim (compare film 15 of ~igure 2).
~ igur~ 6 ~llustrates an embodiment of the
invention ln which all the electrode piates 3~ 4~ 11 are
carri~d by the same dielectric sheet 10 whlch i8 of clear
gla~ As befvre, the dl~charging slaYe electrodes 4
arc connected by conductors 5 to terminal ~ 6 at -the ~ide3
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. of the panel, but in this case those conductors and
t0rminals are applied to glas~ sub~trate 10. A~ i~dexing
~she~et 8 bearing printed indic:la 9 i~ minated to the glass
-- sheet lO by an aclhesive film 15~ and a ~upport shee t 18
5 i~ in turn laminated to the indexing ~heet 8~ again by an
adhes~ve ~ m 15.
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