Two-dimensional electric conductor designed to function as an electric switch

A conductor comprising a first and second electric conducting element, each in the form of a flat plate, and at least a third electric conducting element also in the form of a flat plate. The first and second conducting elements are arranged with one surface contacting a surface on the third conducting element; and a spacer element formed from insulating material is placed between the mating surfacese of two of the aforementioned conducting elements, so as to at least partially shield the aforementioned surfaces. The structure of the material from which the third electric conducting element is formed comprises a supporting matrix formed from flexible, electrically-insulating material and particles of electrically-conductive material scattered in random, substantially uniform manner inside cells on the aforementioned matrix; which cells communicate at least partially with one another, and are at least partially larger in size than the respective particles of electrically-conductive material housed inside the same.

BACKGROUND OF THE INVENTION 
The present invention relates to a two-dimensional electric conductor 
designed to function as an electric switch and enabling the formation of 
an electric circuit comprising any number of electric switches located at 
any point on a flat surface. 
The two-dimensional electric conductor according to the present invention 
is designed to solve the problem of closing an electric circuit by 
applying given pressure at any point on a flat surface. Such performance 
is frequently required in a number of technical applications, e.g. for 
producing an electric signal for activating a relay, for example, and so 
indicating that external pressure is being applied at any point on a 
surface. 
At present, this problem can only be solved approximately, by setting out a 
number of separate switches having their terminals connected to conductors 
on an electric line. Such a system, however, only enables control of a 
limited number of points on the surface. What is more, the said electric 
line is unreliable and involves the use of numerous switches and electric 
conductors, connection of which is both time-consuming and expensive. 
SUMMARY OF THE INVENTION 
The aim of the present invention is to provide a two-dimensional electric 
conductor designed to function as an electric switch, and to solve the 
aforementioned problem without involving any of the aforementioned 
drawbacks. With this aim in view, according to the present invention, 
there is provided a two-dimensional electric conductor, characterised by 
the fact that it comprises a first and second electric conducting element, 
each in the form of a flat plate; and at least a third electric conducting 
element, also in the form of a flat plate; the said first and second 
electric conducting elements being arranged in such a manner that one 
surface contacts a surface on the said third electric conducting element; 
and a spacer element formed from electrically-insulating material being 
arranged between the opposite surfaces of the said third element and at 
least one of the said first and second elements, so as to at least 
partially shield the said two surfaces; the structure of the material from 
which the said third electric conducting element is formed comprising a 
supporting matrix formed from flexible, electrically-insulating material 
and particles of electrically-conductive material scattered in random, 
substantially uniform manner inside cells on the said matrix; said cells 
communicating at least partially with one another, and being at least 
partially larger in size than the respective particles of 
electrically-conductive material housed inside the same. 
The structure of the said material from which the said third electric 
conducting element is formed is as described in U.S. patent application 
Ser. No. 07/145,612, filed Jan. 19, 1988, by the present Applicant and 
entitled: "Electric resistor designed for use as an electric conducting 
element in an electric circuit, and relative manufacturing process", to 
which the reader is referred for further details. The entire disclosure of 
U.S. patent application Ser. No. 07/145,612 is incorporated herein by 
reference.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to FIG. 1, the two-dimensional electric conductor according 
to the present invention is substantially in the form of a flat plate, and 
comprises a first and second electric conducting element 1 and 2, and at 
least a third electric conducting element 3, each in the form of a flat 
plate. In the FIG. 1 embodiment, provision is made for a pair of third 
conducting elements 3a and 3b. The said conducting elements are arranged 
one on top of the other, so as to form a structure in which upper surface 
4 of element 3a contacts lower surface 5 of element 1, and lower surface 6 
of element 3b contacts surface 7 of element 2. Between surfaces 8 and 9 of 
elements 3a and 3b, there is provided a spacer element 10 formed from 
electrically-insulating material; and on the outer surfaces of elements 1 
and 2, there are provided layers of insulating material 12 and 13. 
The material of the said third conducting element (3a and 3b in the FIG. 1 
embodiment) presents a structure comprising a supporting matrix 14 (FIG. 
2) formed from flexible, electrically-insulating material, and particles 
15 of electrically-conductive material scattered in random, substantially 
uniform manner inside cells in the said matrix. The said cells 
communicate, at least partially, with one another, and are, at least 
partially, larger than the respective particles of electrically-conductive 
material housed inside the same, so as to define gaps 16 between the 
surfaces of particles 15 and the said cells. 
A material presenting the aforementioned structure is described in U.S. 
patent application Ser. No. 07/145,612, filed Jan. 19, 1988, by the 
present Applicant and entitled: "Electric resistor designed for use as an 
electric conducting element in an electric circuit, and relative 
manufacturing process." 
As stated in the aforementioned Patent Application, the said material is 
electrically conductive, and presents the favourable property of 
increasing in electrical conductivity as increasing pressure is applied on 
it. Such favourable performance is due to improved electrical conductivity 
of chains of particles 15. In fact, as increasing pressure is applied on 
the material, this improves the conductivity of chains of contacting 
particles 15, while at the same time rendering conductive any chains of 
non-contacting particles 15, when sufficient pressure is applied for 
reducing or eliminating gaps 6 between the said non-contacting particles 
15. Conducting elements 1 and 2 may be formed from wire mesh. 
To enable a clearer understanding of the process according to which the 
third conducting elements 3a and 3b are formed, a description will first 
be given of the structure of the resistor so formed. 
The structure of the resistor is as shown in FIGS. 5 and 6, which show 
sections of a portion of the resistor enlarged a few hundred times. 
The said resistor substantially comprises a supporting matrix 214, formed 
from flexible, electrically insulating material, and particles 215 of 
electrically conductive material arranged in substantially uniform manner 
inside corresponding cells 230 on the said matrix 214. As in the 
embodiment shown, the said particles preferably consist of granules of 
electrically conductive material. As shown in the larger-scale section in 
FIG. 6, at least some (e.g. 50 to 90%) of the said cells communicate with 
one another, and in a number of cases, are exactly the same shape and size 
as the granules contained inside. Other cells, on the other hand, are 
slightly larger than the said granules, so as to form a minute gap 216 
between at least part of the outer surface of the granule and the 
corresponding inner surface portion of the respective cell. 
The arrangement of cells 230, and therefore also of granules 215, inside 
matrix 214 is entirely random. Though the advantages of the resistor 
according to the present invention are obtainable even if only a few of 
cells 230 communicate with one another, it is nevertheless preferable for 
most of them to do so. For best results, the estimated percentage of 
communicating cells is around 50-90%. 
Though conducting granules 215 may be of any size, this conveniently ranges 
between 10 and 250 microns. Likewise, granules 15 may be of any shape and, 
in this case, are preferably irregular, as shown in FIGS. 5 and 6. 
Matrix 214 may be formed from any type of electrically insulating material, 
providing it is flexible enough to flex, when a given pressure is applied 
on the resistor, and return to its original shape when such pressure is 
released. Furthermore, the material used for the matrix must be capable of 
assuming a first state, in which it is sufficiently liquid for it to be 
injected into a granule structure statistically presenting each of the 
said granules arranged at least partially contacting the adjacent granules 
with which it defines a number of gaps; and a second state in which it is 
both solid and flexible. The viscosity of the liquid material conveniently 
ranges from 500 to 10,000 centipoise. 
Matrix 214 may conveniently be formed from synthetic resin, preferably a 
synthetic thermoplastic resin, which presents all the aforementioned 
characteristics and is thus especially suitable for injection into a 
granule structure of the aforementioned type. 
Though the size of granules 215, which depends on the size of the resistor 
being produced, is not a critical factor, the said granules are preferably 
very small, ranging in size from 10 to 250 microns. 
The conducting material used for the granules may be any type of metal, 
e.g. iron, copper, or any type of metal alloy, or non-metal material, such 
as graphite or carbon. The materials for matrix 214 and granules 215 may 
thus be selected from a wide range of categories, providing they present 
the characteristics already mentioned. 
The material employed for matrix 214 which, as already stated, must be 
flexible and insulating, is preferably, though not necessarily, so 
precompressed inside matrix 214 itself as to exert sufficient pressure on 
particles 215 to maintain contact between the same. It follows, therefore, 
that each minute element of the said matrix 214 material is in a 
sufficiently marked state of triaxial precompression as to exert on 
adjacent elements, in particular particles 215, far greater stress, for 
producing contact pressure between the surfaces of the said particles, 
than if the said triaxial precompression were not provided for. As will be 
made clearer later on, such a state of triaxial precompression is a direct 
consequence of the process according to the present invention. 
With the structure described and shown in FIGS. 5 and 6, the resistor 
according to the present invention presents an extremely large number of 
granules 215 of conducting material, which granules either contact one 
another, or are separated from adjacent granules by extremely small gaps 
216 which may be readily bridged when given pressure is applied on the 
resistor. This results in the formation, inside the said structure, of a 
number of electrical conductors, each consisting of a chain comprising an 
extremely large number of granules 215, which are normally already 
arranged contacting one another inside the said structure. Each of the 
said chains may electrically connect end surfaces 50 and 60 on the 
resistor directly, as shown by dotted line C1 in FIG. 5. Alternatively, 
chains may be formed inside the resistor, as shown by dotted line C2 in 
FIG. 5, in which the individual granules in the chain are partly arranged 
contacting one another directly, and partly separated solely by gaps 216. 
The granules in such chains may be brought into contact, as in the case of 
chain C1, by subjecting surfaces 50 and 60 on the resistor to a given 
pressure sufficient to flex the material of matrix 214 so bridge the said 
gaps for bringing the adjacent granules separated by the same into direct 
contact. 
The process according to the present invention is as follows. 
The first step is to prepare a homogeneous system comprising particles, 
preferably granules, of a first electrically conductive material arranged 
in substantially uniform manner inside a mass of a second liquid material 
which, when solidified, is both electrically insulating and flexible. The 
mass of the said second liquid material is then solidified to form a 
supporting matrix for the granules. According to the present invention, 
throughout solidification of the said second material, a given pressure is 
applied on the system for the purpose of producing triaxial precompression 
of the said second material when solidified. Such pressure, which is 
maintained substantially constant throughout solidification, ranges from a 
few tenths of a N/mm.sup.2 to a few N/mm.sup.2. 
For forming the said homogeneous system, a granule structure is first 
formed, which structure statistically presents each granule arranged at 
least partially contacting the adjacent granules, with which it defines a 
number of gaps which are then injected with the said second liquid 
material. The said second material may be liquified by simply heating it 
to a given temperature. For solidifying it, cooling is usually sufficient. 
In the case of synthetic resins, however, these must be solidified by 
means of curing. 
The process according to the present invention may comprise the following 
stages. 
A first stage, in which a mass of electrically conductive granules 116 is 
formed, for example, inside an appropriate vessel 115 (FIG. 12). For this 
purpose, the granules, after being poured into the said vessel, are 
vibrated so as to enable settling. The bottom of vessel 115 is 
conveniently either porous or provided with holes for letting out the air 
or gas trapped between the granules. 
A second stage, as shown in FIG. 13, in which the mass of granules 116 is 
compacted by subjecting it to a given pressure, e.g. by means of piston 
117, applied in any appropriate manner on the upper surface of mass 116. 
This produces a granule structure in which, statistically, at least part 
of the surface of each granule is arranged contacting surface portions of 
the adjacent granules, with gaps inbetween. 
As shown in FIG. 13, piston 117 is conveniently provided with a tank 118 
containing the said second material in liquid form; which liquid material 
may be forced, e.g. by a second piston 119, through hole 120 into a 
chamber 121 defined between the upper surface of granules 116 and the 
lower surface of piston 117 as shown clearly in FIG. 14. The said second 
liquid material in tank 118 is a material which may be solidified and, 
when it is, is both insulating and flexible. In the event the said 
material is liquified by heating, appropriate heating means (not shown) 
are also provided for. 
A third stage (FIGS. 14 and 15) in which piston 119 moves down and piston 
117 up, so as to force a given amount of the said second liquid material 
inside chamber 121 (FIG. 14). Piston 117 is then brought down for 
producing a given pressure inside the liquid material in chamber 121 and 
so forcing it to flow into the gaps between the granules in mass 116 and 
form, with the said granules, the said homogeneous system. At the same 
time, any air between the granules is expelled through the porous bottom 
of vessel 115. The pressure produced by piston 117, at this stage, inside 
the liquid material mainly depends on the size of the granules, the 
viscosity of the liquid, the height of the granule mass being impregnated, 
and required impregnating time. 
Penetration of the liquid material inside the gaps in granule mass 116 has 
been found to have no noticeable effect on the granule arrangement 
produced in the compacting stage. 
A fourth stage (FIG. 15) in which the homogeneous system of granules and 
liquid material produced in the foregoing stage is substantially 
solidified. This may be achieved by simply allowing the system to cool and 
the said second liquid material to set. At this stage, changes may be 
observed in the structure of the said second material due, for example, to 
curing of the same. 
It has been found necessary to dose the liquid material fed into chamber 
121 prior to the injection stage, in such a manner as to ensure that it is 
sufficient to impregnate only a large part of granule mass 116 leaving a 
nonimpregnated layer 122 (e.g. of about 25%). In like manner, the liquid 
material flowing inside the gaps between the granules is subjected solely 
to atmospheric pressure through the porous bottom of vessel 115. The 
granules, on the other hand, (be they impregnated or not), are subjected 
to the pressure exerted by piston 117, as shown in FIG. 16. The said 
pressure is applied evenly over all the contact points between adjacent 
granules, and is what determines the specific electrical resistance of the 
resulting material. That is to say, using the same type of granules and 
liquid material, an increase in the said pressure results, within certain 
limits, in a reduction of the specific electrical resistance of the 
resulting material. The said pressure must be maintained constant until 
the liquid material has set, and must be at least equal or greater than 
the compacting pressure applied in stage 2 (FIG. 13). 
Though the said pressure may be selected from within a very wide range, 
convenient pressure values have been found to range from a few tenths of a 
N/mm.sup.2 to a few N/mm.sup.2. For resistors prepared as described in the 
following examples, the following pressures were selected: 
Example 1 : 1.17 N/mm.sup.2 
Example 2 : 0.62 N/mm.sup.2 
Example 3 : 1.56 N/mm.sup.2 
Example 4 : 2.35 N/mm.sup.2 
Example 5 : 1.17 N/mm.sup.2 
The mass of material so formed inside vessel 115 may be cut, using standard 
mechanical methods, into any shape or size for producing the electric 
resistor according to the present invention. 
To those skilled in the art it will be clear that changes may be made to 
both the resistor and the process as described and illustrated herein 
without, however, departing from the scope of the present invention. 
In particular, granules 215 arranged inside matrix 214 may be replaced by 
particles of electrically conductive material of any shape or size, e.g. 
short fibres. 
For preparing the said homogeneous system comprising particles of a first 
electrically conductive material distributed inside a mass of a second 
liquid material which, when solidified, is both electrically insulating 
and flexible, processing stages may be adopted other than those described 
with reference to FIGS. 12 to 16. 
The said homogeneous system, in fact, may be obtained by mixing the said 
particles mechanically with the said second liquid material, using any 
appropriate means for the purpose. 
According to the aforementioned variation, throughout solidification of the 
said second material, the said system is forced against a porous (or 
punched) septum for letting out, through the said septum, at least part of 
the said second liquid material. The pressure so produced may be 
maintained until the said second material solidifies, so as to produce the 
said triaxial precompression in the solidified said second material. 
For achieving the said precompression, the said system may be spun 
throughout solidification of the said second liquid material. 
When incorporated in an electric circuit, performance of the resistor 
according to the present invention is as follows. 
If no external pressure is applied on the resistor, and end surfaces 50 and 
60 are connected electrically via appropriate conductors, electric current 
may be fed through the resistor as in any type of rheophore. The density 
of the current feedable through the resistor has been found to be very 
high, at times in the region of ten A/cm.sup.2. When idle, the resistance 
of the resistor according to the present invention may, therefore, be low 
enough to produce an electrical conductor capable of handling a high 
current density, as required for supplying a circuit component or device. 
A number of resistance values relative to resistors produced by 
appropriately selecting the characteristics of the particles and the 
material of matrix 214, and the parameters of the present process, are 
shown in the Examples given later on. 
Total resistance of the resistor so formed has been found to be constant, 
and dependent solely on the structure of the resistor, in particular, the 
number and size of communicating cells 230 in matrix 214, and the number 
of gaps 216 separating adjacent granules 215. 
By appropriately selecting the aforementioned parameters, some of which 
depend on the process described, a resistor may be produced having a given 
prearranged resistance. When pressure is applied perpendicularly to 
surfaces 50 and 60, the electrical resistance measured perpendicularly to 
the said surfaces is reduced in direct proportion to the amount of 
pressure applied. FIGS. 7 to 10 show four resistance-pressure graphs by 
way of examples and relative to four different types of resistors, the 
characteristics of which will be discussed later on. As shown in the said 
graphs, the fall in resistance as a function of pressure is a gradual 
process represented by a curve usually presenting a steep initial portion. 
Even very light pressure, such as might be applied manually, has been 
found to produce a considerable fall in resistance. In the case of a 
resistor having the resistance-pressure characteristics shown in FIG. 10, 
starting resistance was reduced to less than one percent by simply 
applying a pressure of around 1 N/mm.sup.2 (about 10 kg/cm.sup.2). With a 
different structure and pressures of around 2 N/mm.sup.2 (about 20 
kg/cm.sup.2), starting resistance may be reduced by 1/3 (as shown in the 
FIG. 7 graph). 
If the pressure applied on the resistor according to the present invention 
is maintained constant (or zero pressure is applied), electrical 
performance of the resistor has been found to conform with both Ohm's and 
Joule's law. For application purposes, it is especially important to 
prevent the heat generated inside the resistor (Joule effect) from 
damaging the structure. This obviously entails knowing a good deal about 
the thermal performance of the material from which the supporting matrix 
is formed. 
Assuming the resistor according to the present invention is capable of 
withstanding an average maximum temperature of 50.degree. C., under normal 
heat exchange conditions with an ambient air temperature of 20.degree. C., 
the density of the current feedable through the resistor ranges from 0.2 
A/cm.sup.2 (Example 4) to 11 A/cm.sup.2 (Example 5) providing no external 
pressure is applied. 
In the presence of external pressure, such favourable performance of the 
electric resistor according to the present invention is probably due to 
improved electrical conductivity of granule chains such as C1 and C2 in 
FIG. 5. In fact, as pressure increases, the conductivity of 
contacting-granule chains (such as C1) increases due to improved 
electrical contact between adjacent granules, both on account of the 
pressure with which one granule is thrust against another, and the 
increased contact area between adjacent granules. In addition to this, 
granule chains such as C2, in which the adjacent granules are separated by 
gaps 216, also become conductive when a given external pressure is applied 
for bridging the gaps between adjacent pairs of otherwise non-conductive 
granules. 
Total electrical conductivity of the granule chains increases gradually 
alongside increasing pressure by virtue of matrix 14 being formed from 
flexible material, and by virtue of the said material being precompressed 
triaxially. As a result, adjacent granules separated by gaps 216 are 
gradually brought together, and the contact area of the granules already 
contacting one another is increased gradually as flexing of the matrix 
material increases. Each specific external pressure is obviously related 
to a given resistor structure and a given total conducting capacity of the 
same. When external pressure is released, the resistor returns to its 
initial unflexed configuration and, therefore, also its initial resistance 
rating. 
In the said initial unflexed configuration, the electrical performance of 
the material the resistor is made of has been found to be isotropic, in 
the sense that the specific resistance of the material is in no way 
affected by the direction in which it is measured. If, on the other hand, 
the material the resistor according to the present invention is made of is 
flexed by applying external pressure in a given direction, the specific 
resistance of the material has been found to vary continuously in the said 
direction, depending on the amount and direction of the flexing pressure 
applied. 
To illustrate the electrical performance of the resistor according to the 
present invention, when subjected to varying external pressure, four 
resistors featuring different structural parameters will now be examined 
by way of examples. 
A fifth example will also be examined in which the specific resistance of 
the resistor according to the present invention is sufficiently low for it 
to be considered a conductor. 
EXAMPLE 1 
A cylindrical resistor, 12.6 mm in diameter and 7.4 mm high was prepared, 
as shown in FIGS. 12 to 16, using epoxy resin (VB-BO 15) for matrix 214. 
Conducting granules 215 consisted of carbon powder ranging in size from 200 
to 250 microns. 
On resistors with granules of this sort, the matrix insulating material 
injected between the granules occupies approximately 56.8% of the total 
volume of the resistor. The resistor so formed was connected to the 
electric circuit in FIG. 11 in which it is indicated by number 110. The 
said circuit comprises a stabilized power unit 111 (with an output 
voltage, in this case, of 4.5 V), a load resistor 112 (in this case, 10 
ohm), and a digital voltmeter 113, connected as shown in FIG. 11. Resistor 
110 was subjected to pressures ranging from 7.8.multidot.10.sup.-2 
N/mm.sup.2 to 196.multidot.10.sup.-2 N/mm.sup.2. 
Resistance was measured by measuring the difference in potential at the 
terminals of resistor 112 using voltmeter 113, and plotted against 
pressure as shown in the FIG. 7 graph. From a starting figure of 5.4 Ohm, 
resistance gradually drops down to 1.78 Ohm as the said maximum pressure 
is reached. 
EXAMPLE 2 
A cylindrical resistor, 12.6 mm in diameter and 7.2 mm high was prepared as 
before using an alpha-cyanoacrylatebase resin for matrix 214 and carbon 
granules ranging in size from 200 to 250 microns. 
Once again, the resistor was connected to the FIG. 11 circuit, the 
components of which presented the same parameters as in Example 1. The 
relative resistance-pressure graph is shown in FIG. 8, which shows a 
resistance drop from 16 to 5.25 Ohm between the same minimum and maximum 
pressures as in Example 1. 
EXAMPLE 3 
A tubular resistor with an outside diameter of 12.6 mm, an inside diameter 
of 3.5 mm, and 5.4 mm high was prepared as before, using epoxy resin 
(VB-BO 15) for the matrix and iron granules ranging in size from 50 to 150 
microns. On resistors with granules of this sort, the matrix insulating 
material injected between the granules occupies approximately 55% of the 
total volume of the resistor. Resistance was again measured as shown in 
FIG. 11 using a 1000 Ohm load resistor 112 and 4.5 V power unit 111. 
Pressure was adjusted gradually from 59.multidot.10.sup.-2 N/mm.sup.2 to 
7.22 N/mm.sup.2 to give the graph shown in FIG. 9, which shows a 
resistance drop from 1790 to 493 Ohm between minimum and maximum pressure. 
EXAMPLE 4 
A 2.4 mm high tubular resistor having the same section as in Example 3 was 
prepared as before, using silicon resin for matrix 214 and iron granules 
ranging in size from 50 to 150 microns. 
Resistance was again measured on the FIG. 11 circuit, using a 100 Ohm load 
resistor 112 and a 1.2 V power unit 111. Pressure was adjusted from 
4.2.multidot.10.sup.-2 N/mm.sup.2 to 119.multidot.10.sup.-2 N/mm.sup.2 to 
give the graph shown in FIG. 10 which shows a resistance drop from 1100 to 
8.1 Ohm between minimum and maximum pressure. 
EXAMPLE 5 
A 3.4 mm high tubular resistor having the same section as in Example 4 was 
prepared as before, using epoxy resin (VB-ST 29) for matrix 214 and tin 
granules ranging in size from 50 to 200 microns. 
Resistance, measured in the absence of external pressure between the two 
bases of the tubular-section cylinder, was 0.08 Ohm. The specific 
resistance of the resistor material, in this case, therefore works out at 
0.27 Ohm.cm, which is low enough for the resistor to be considered a 
conductor. Assuming heat (Joule effect) is dissipated by normal heat 
exchange in air at a temperature of 20.degree. C., and the maximum 
temperature withstandable by the resistor is 50.degree. C., the density of 
the current feedable through this resistor is approximately 11 A/cm.sup.2. 
Instead of a pair of conducting elements 3a and 3b formed from the said 
material, the conductor in the FIG. 3 embodiment comprises only one such 
element 17. The FIG. 3 embodiment presents the same conducting elements as 
in the previous embodiment, which elements are indicated using the same 
numbering system, and spacer element 10 is located between elements 17 and 
2 as shown clearly in FIG. 3. 
In the FIG. 4 embodiment, conducting elements 1 and 2 are formed in such a 
manner as to define a number of strips arranged alternately and 
substantially in the same plane, so as to present adjacent strips 
pertaining to different elements. Spacer element 10 is located between the 
said strips and the third conducting element which, in this case, is 
numbered 18 and consists of a flexible pad 18a, formed from the same 
conducting material as element 3 in the FIG. 1 embodiment, and a 
conducting mesh 18b having no external electrical connections. Spacer 
element 10 may, as in the previous case, be formed from a mesh of 
insulating material. 
The two-dimensional electric conductor according to the present invention 
may be connected to an electric circuit comprising a current source, of 
which terminals 19 are shown in the attached drawings, and a user device, 
such as a relay 20. 
The said circuit is formed so as to connect the said components to 
conducting elements 1 and 2, as shown in the attached drawings. When so 
arranged, and when no pressure is applied on the outer surfaces of the 
two-dimensional electric conductor according to the present invention, the 
said circuit is maintained open and current prevented from circulating 
inside the same by virtue of spacer element 10, which separates the 
surfaces of the conducting elements facing the respective surfaces of 
spacer element 10 itself. 
When, on the other hand, pressure is applied on a given portion 21 (FIG. 2) 
of at least one of the outer surfaces of the conductor according to the 
present invention, this produces localised flexing of the said portion of 
the third conducting element (3a, 3b, 17 or 18), thus causing a surface of 
the said conducting element to contact the respective surface of the 
adjacent conducting element. Should both conducting elements 3a and 3b in 
the FIG. 1 embodiment be flexed, this results in contact between portions 
21 of surfaces 8 and 9 (FIG. 2), thus closing the electric circuit and 
allowing current to circulate inside the same, for activating user device 
20. As shown clearly in FIG. 2, closure of the circuit is made possible by 
surfaces 8 and 9 contacting on the portion left exposed by spacer element 
10. 
The same applies also to the conductors in the FIG. 3 and 4 embodiments, in 
the first of which, flexing of element 17 produces electrical contact 
between element 17 and the underlying conducting element 2, and, in the 
second, contact is established between two of the adjacent strips of 
conducting elements 1 and 2. 
In addition to conducting current, the two-dimensional electric conductor 
according to the present invention clearly also provides for forming an 
infinite number of electric switches, each of which may be activated by 
pressure applied on any given point on the conductor itself. Furthermore, 
by virtue of the material of the said third conducting element increasing 
in conductivity alongside increasing pressure, the said pressure, in 
addition to closing the said circuit, also provides for producing a signal 
proportional to the amount of pressure applied. 
To those skilled in the art it will be clear that changes may be made to 
the embodiments described and illustrated herein without, however, 
departing from the scope of the present invention.