United States Patent [19]
`Hurst et al.
`
`[54]
`[75]
`
`[731
`[22]
`121]
`
`[52]
`[51]
`[53]
`
`[56]
`
`DISCRIMINATING CONTACT SENSOR
`lnventors: George S. Hurst; William C.
`Colwell, Jr., both of Oak Ridge,
`Tenn.
`Assignee: Elographics, Inc., Oak Ridge, Tenn.
`Filed:
`Mar. 18, 1974
`Appl. No.: 452,784
`
`US. Cl. ............................... .. 178/18; 200/86 R
`lnt. Cl.2 ................... .. H01H 43/08; H04N 1/00
`Field of Search ..... .. 200/86 R, 153 M, 46, 159;
`178/18, 19, 20; 33/1 M; 340/272
`
`References Cited
`UNITED STATES PATENTS
`
`3,617,666
`3,632,874
`3,668,337
`3,722,086
`
`Braue .............................. .. 200/86 R
`11/1971
`Malavard et al..
`1/1972
`6/1972 Sinclair ........................... .. 200/86 R
`3/1973 Wikkerink et al. ............. .. 200/86 R
`
`[11]
`[451
`
`3,911,215
`Oct. 7, 1975
`
`Primary Examiner—Thomas A. Robinson
`Attorney, Agent, or Firm—Martin J. Skinner
`
`ABSTRACT
`[ 5 7 ]
`A sensor construction is described for normally main
`taining two juxtaposed electrical potential carrying
`sheets, at least one being ?exible, separated from each
`other but permitting contact therebetween when an
`object of speci?ed radius of curvature is pressed
`against the ?exible sheet. The separation of the sheets
`is accomplished by producing discrete small buttons of
`insulation, preferably on the ?exible sheet, with the
`spacing and the height of the buttons determining the
`largest radius of curvature to which the sensor will re
`spond. This construction is speci?cally applied to a
`telescriber sensor or the like whereby contact is made
`only by depression of the ?exible sheet with a writing
`instrument and not by any portion of a writer’s hand.
`
`6 Claims, 5 Drawing Figures
`
`Samsung USP 7,973,773
` Exhibit 1014 Page 1
`
`

`
`US. Patent‘ ‘0a. 7,1975
`
`Sheet 110m
`
`3,911,215
`
`+
`
`__
`
`VOLTAGE
`SOURCE
`
`SAMPLE AND
`HOLD
`
`X-ANALOG
`
`7
`OSCILLATOR
`
`F|G.1
`(Prior Ar’r)
`
`+ ....
`
`VOLTAGE
`SOURCE
`
`19
`
`SAMPLE AND
`HOLD
`
`Y-ANALOG
`
` Exhibit 1014 Page 2
`
`

`
`US. Patent 0a. 7,1975
`
`Sheet 2 of2
`
`3,911,215
`
`T4
`
`8
`
`25
`
`24
`
`FIG.
`
`m _\ x m \ \ m x \ x \ \ \ \ m
`
`24
`
`FlG.4
`
` Exhibit 1014 Page 3
`
`

`
`1
`DISCRINHNATING CONTACT SENSOR
`
`BACKGROUND OF THE INVENTION
`
`3,911,215
`
`2
`
`5
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a schematic diagram of a simpli?ed circuit,
`substantially as found in above-referenced copending
`application (now US. Pat. No. 3,798,370), for the pur
`pose of permitting a description herein of one applica
`tion of our invention;
`FIG. 2 is an enlarged cross sectional drawing illustrat
`ing the most general form of the subject matter of our
`invention;
`-
`FIG. 3 is an enlarged cross sectional view of our in
`vention when contacted by an object of less than a
`speci?ed radius of curvature for a given set of parame
`ters for the insulation;
`FIG. 4 is an enlarged cross sectional view of our in
`vention when contacted by an object of greater than a
`speci?ed radius of curvature; and
`FIG. 5 is an enlarged cross section drawing of an
`electrographic sensor embodying our invention for
`point coordinate determination, written telemetry and
`the like.
`
`DETAILED DESCRIPTION
`
`The underlying principle of our invention may be ex
`plained through the use of FIG. 2 which shows the es
`sential components of the sensor in an enlarged cross
`sectional view. Two substantially planar and parallel
`sheets 23, 24 are assumed to have an electrical poten
`tial applied thereto by any conventional means such as
`described hereinafter. Sheet 23 is ?exible, so
`as to be
`deformable toward the second sheet 24 which may be
`rigid. Typical of the flexible material is “Velostat,” a
`conductive plastic distributed by Customs Materials,
`Inc., of Chelmsford, Mass, or Mylar (E. I. DuPont)
`with an aluminized surface as manufactured by numer
`ous companies. The second sheet may be a conductive
`metal plate or, alternatively, a resistive paper sup
`ported on an appropriate backing. If a resistive sheet is
`utilized, a typical material is resistance paper Type L,
`manufactured by Knowlton Bros, Watertown, N. Y.,
`having a resistance of 1000 to 2000 ohms per square.
`Separating the sheets 23 and 24 are a plurality of dis
`tributed insulation buttons 25 preferably attached, as
`shown, to the ?exible sheet for most applications.
`These buttons are of substantially equal diameter, D,
`and height, H, and may be randomly or uniformly dis
`tributed with a spacing, S, being either an average spac
`ing (if random) or the actual center-to-center
`spacing
`(if uniform). The diameter, D, is very much smaller
`than the spacing, S. In general, a small diameter is de
`sirable, and the height and spacing are chosen for a par
`ticular application of the layered structure. The insulat
`ing buttons 25 may be applied to sheet 23 using one of
`several standard techniques again depending upon the
`dimensions. Typical application methods are air-jet
`spraying, electrostatic spraying, rollers and silk screen
`techniques. The material utilized to form the buttons
`may be, for example, insulating printer’s ink, epoxy
`paint or varnish.
`With the construction shown in FIG. 2, we have de
`termined that the height and spacing (with a small ?xed
`diameter) will affect the manner of deforming sheet 23
`so as to contact sheet 24. We have developed a quanti
`tative relationship for the condition that the two sheets
`can be brought into contact by pressing the ?exible
`sheet with an object. This relationship can be expressed
`in terms of the radius of curvature, R, of the pressing
`
`Our invention relates generally to the insulation of
`one electrical potential carrying sheet from a second
`such sheet except when contact therebetween is pur
`posely desired, and more speci?cally to insulation
`means whereby the sheets are brought into contact
`only by an object having a radius of curvature less than
`a speci?c value, the value being established by the ar
`rangement of the insulation. The invention is illustrated
`as applied to writing sensors useful for the electro
`graphic determination of coordinates of a point or for
`the telemetry of drawings, signatures and the like.
`Typical of the prior art in this ?eld is found in US.
`Pat. No. 3,632,874 issued to L. C. Malavard et al. In
`that patent, and speci?cally FIG. 9, a conductive sheet
`of ?exible material is separated only by an air space
`from a second surface or sheet to which is applied or
`thogonal electrical ?elds. A writing instrument is used
`to bring the sheets together and thereby generate x
`and y-related signals as the writing instrument is
`moved. However, it may be seen that ?nger tips,
`knuckles, the edge of the hand, or other objects could
`deform the ?exible sheet and give rise to erroneous
`output signals.
`In copending application Ser. No. 244,629, now US.
`Pat. No. 3,798,370, issued to G. S. Hurst on Mar. 19,
`1974, a sensor is described in which a “deformable”
`insulation is utilized between a ?exible conductive
`grounding sheet and a resistive sheet having the orthog
`onal electric ?elds. In one embodiment a gel separates
`the layers. Although the gel provides the necessary in
`sulation between the sheets, it is not a practical solution
`for production units because of the care required to
`produce a reproducible characteristic. A second em
`bodiment, in the form of a nylon net or the like, is ame
`nable to the production of sensors and is satisfactory
`for many applications of the sensor. However, when
`handwriting is performed on the sensors fabricated
`using the net, the nonuniform thickness (the threads
`versus the knots) of even the ?nest available net mate
`rial may be felt during the writing. Also, movement of
`the net between the layers gives rise to gradual deterio
`ration of the materials in contact therewith.
`
`25
`
`35
`
`45
`
`50
`
`55
`
`SUMMARY OF THE INVENTION
`
`Our invention in its simplest form utilizes a distribu
`tion of small discrete insulating buttons of uniform
`height to normally separate two electrical potential car
`rying sheets where at least one of the sheets is ?exible.
`The buttons may be either uniformly or randomly dis
`tributed and are preferably affixed to the ?exible sheet.
`The spacing and height of the insulating buttons are
`chosen, assuming a ?xed diameter, so as to prevent
`contact of the layers by an object having a radius of
`curvature greater than a selected value and thereby dis
`criminate between objects of different radii of curva
`ture. Speci?cally, the dimensions are chosen to permit
`contact between the layers upon deformation by a con
`ventlonal writing instrument but prevent contact by
`anv part of a hand holding the writing instrument. In
`this structure we eliminate any physical or psychologi
`cal deterrents to normal handwriting.
`
`65
`
` Exhibit 1014 Page 4
`
`

`
`3,911,215
`
`10
`
`20
`
`25
`
`30
`
`35
`
`3
`object using the equation R zSZ/SH. An object having
`a radius of curvature smaller than the value of S 2/8H
`will bring about contact of the layers, as shown in
`FIG. 3. In contrast, an object of radius of curvature
`greater than S‘l/SH will not bring about contact, as
`illustrated in FIG. 4.
`This characteristic of discrimination by the structure
`as to the radius of curvature may be used, for example,
`to determine the number of particles of a given size
`range that impinge against the ?exible layer 23. Thus,
`the structure would be used as a switch in a conven
`tional electrical counting system. The use of several
`sensors each having a discrimination corresponding to
`different values of R would provide an electrical count
`ing system capable of counting the number of imping
`ing particles having various radii of curvature.
`Our invention, however, is of particular value in tel
`emetry sensors and coordinate determining sensors.
`Typical of such sensors is that described in the afore
`mentioned copending patent application of G. S. Hurst.
`This may be understood by referring to FIG. 1 which
`is a schematic circuit diagram of that patent applica
`tion, and to FIG. 5 which is an enlarged cross section
`of a sensor embodying our present invention for use
`with the circuit of FIG.
`1. Referring ?rst to FIG. 1, a
`uniform highly resistive sheet 10 is suitably mounted by
`any conventional means to a support (not shown) so as
`to form a plane. In each comer of sheet 10 are spot
`electrodes 11 as at points A, B, C, and D. Spacedbe
`tween the corner spot electrodes, in a row-like manner,
`are edge spot electrodes 12 along each edge of sheet
`10. Three edge electrodes are shown along each edge
`for illustration; an actual sensor may have more or less
`for a particular size and application.
`Connected between adjacent spopt electrodes 11 and
`12 are individual discrete high precision (e.g., 0.1 to
`1.0%) resistors 13. These resistors 13, in series along
`each edge, form four resistor networks
`joined to elec
`trodes 11 at points A‘, B, C and D. It will be recognized
`that this structure, using discrete resistors, permits the
`choice of preferred precision resistive elements to as
`sist in the establishment of uniform electrical gradients
`in the resistive paper 10.
`The ends of each resistor network are connected, in
`an appropriate sequence, to a voltage source 18 or 19
`by appropriate switches such as 14a, 14b, etc., in order
`_to achieve orthogonal electric ?elds. Although a single
`switch across each network would function, in the same
`manner, solid state switches required for rapid opera
`tion (e.g., 104-105 Hz) often exhibit ohmic resistance
`in the closed position. However, the resistance of each
`of the contacts of a chip of four switches is substantially
`equal and thus the circuit as shown overcomes the ef
`fect of differing internal resistance. Operation of the
`switches l4—l7 is governed by the output signals of os
`cillator 20.
`Further details of the electrical circuit may be found
`in the cited copending application (now US. Pat. No.
`3,798,370). The operation of the circuit results in uni-‘
`form orthogonal electric ?elds being generated in resis
`tive sheet 10 during mutually exclusive time periods.
`Accordingly, when any speci?c electrical potential
`(such as an electrical ground) is applied at a point on
`the resistive sheet, as by bringing sheet 23 into contact
`with sheet 10,
`output signals are produced that are re
`lated to the x- and y-coordinates of the point. The coor
`dinates are sampled at the rate of the oscillator; thus,
`
`40
`
`45
`
`55
`
`60
`
`65
`
`4
`the coordinates of a “moving point” may be followed
`from the signals generated at the output of conven
`tional sample-and-hold circuits 21,
`22. These sample
`and-hold circuits maintain the signal due to one coordi
`nate while the other coordinate signal is being mea
`sured and then update the signal with new values.
`In practice, the resistive sheet 10 is made a portion
`of a sensor unit such as illustrated in FIG. 5. This shows
`the sheet 10 and an electrode 12 mounted within a case
`26. Spaced above resistive sheet 10, and parallel
`thereto, is the ?exible conductive sheet 23 such as
`formed from aluminzed Mylar or the like. The ?exible
`layer 23 is normally separated by the insulator buttons
`25 from the resistive sheet 10 as described herein
`above. Placed upon the ?exible sheet 23 is a protective
`cover sheet 27. Any conventional writing instrument
`28, such as a ball-point pen or pencil, may be moved
`over the surface of the cover sheet 27, or another sheet
`(not shown) laid thereon, so as to depress the ?exible
`sheet 23 to bring about contact with the resistive sheet
`10 thus initiating electrical signals corresponding to the
`coordinates of the contact point.
`In order that the writing instrument 28, if moved con
`tinuously on the sheet 27, will not be above an insulat
`ing button25 more than about 1%.of the time, a maxi
`mum button size (diameter) of less than 0.005 in.
`(0.125 mm) is preferred. With this condition, the time
`of interruption of electrical contact between sheets 10
`and 23 during continuous writing will be much less than
`1%. The spacing between buttons 25 should be much
`greater than the diameter of the buttons and for this ap
`plication may be in a range of about 0.025 to 0.075 in.
`(0.635 - 1.9 mm). The height of the buttons, if less
`than about 0.005 in. (0.125 mm) cannot be felt as writ~
`ing occurs. In order to provide reasonable discrimina
`tion between pressure of a writing instrument and por
`tions of a writer’s hand, the above-cited equation, R z
`52/ 8H, may be used to determine the value of R for var
`ious values of separation, S, and height, H. For exam
`ple, if S = 0.030 in. (0.66 mm) and H = 0.001 in.
`(0.025 mm) then R equals about 0.1 in. (2.54 mm).
`With S = 0.050 and H= 0.002 in. (1.27 and 0.05 mm,
`respectively), R becomes 0.15 in. (3.8 mm). Either of
`these values are sufficiently small such that the portions
`of a writer’s hand will not cause contact between the
`?exible sheet 23 and the resistive sheet 10. However,
`an instrument like a ball-point pen with a radius of cur
`vature of about 0.025 in. (0.635 mm) will readily cause
`contact as it moves across the surface except when over
`a button ( 1% or less of the surface). Accordingly, con
`tinuous writing may be performed with output signals
`being derived continuously that are proportional to the
`writing instrument position.
`The output signals of the circuit may be utilized in
`many ways. For example, if the sensor is utilized for sig
`nature veri?cation, the signals may be transmitted to a
`remote stationwhere a duplicate of the signature may
`be produced using conventional equipment (e.g., an
`oscilloscope). Alternatively, the signals may be com
`pared with signals held in storage in a computer for ver
`i?cation of the identity.
`In another utilization, data points on graphs and the
`like may be digitized, displayed, reproduced and/or
`stored. This would apply also to storage of information
`related to sketches of proposed design of an apparatus
`part, etc., until a ?nal design is completed. Further
`more, output signals derived from data may be pro
`
` Exhibit 1014 Page 5
`
`

`
`3,911,215
`
`5
`
`15
`
`5
`cessed by a programmed calculator to compute desired
`information.
`Having described several applications for our inven
`tion, it will become apparent to those versed in the art
`that the basic sensor has many applications. We mean,
`by the term basic sensor, a composite of a pair of
`sheets, each being capable of carrying an electrical po
`tential and at least one being ?exible, separated by
`small discrete buttons of insulating medium. The pre
`ferred dimensions of the insulating buttons will vary ac
`cording to the utilization of our discriminating sensor.
`For most applications, one of the layers will be a resis
`tive sheet in which may be established orthogonal elec
`tric ?elds. Although we prefer applying the present in
`vention to the sensor of the cited copending application
`(now U.S. Pat. No. 3,798,370), it may be applied to
`sensors such as those described in US. Pat. Nos.
`3,632,874, 3,449,516, 3,670,103, etc.
`1 claim:
`1. A discriminating contact sensor which will respond
`only to‘a contacting object having a radius of curvature
`less than a speci?c value, which comprises: a ?rst sheet
`of a ?exible material capable of being energized to es
`tablish an electrical potential thereon, a second sheet
`capable of being energized to establish an electrical po
`tential thereon in juxtaposition with the ?rst sheet, and
`a plurality of substantially uniform discrete insulating
`buttons electrically separating the ?rst and second
`sheets throughout the sensor, the buttons having a
`height and an average spacing whereby the maximum
`30
`radius of curvature of the object to which the sensor
`will respond is approximately equal to the square of the
`average spacing between the buttons divided by eight
`times the height of the buttons.
`2. The sensor of claim 1 wherein the insulating but
`tons are substantially circular in a section parallel to
`the ?rst and second sheets and have a diameter from
`
`6
`about 0.001 to about 0.015 in., an average spacing be
`tween adjacent buttons of from about 0.025 to about
`0.075 in. and a height in a direction perpendicular to
`the ?rst and second sheets of from about 0.0005 to
`about 0.015 in.
`3. An improved electrographic sensor for writing
`thereon of the type wherein a uniform resistive sheet
`having electrodes attached thereto for the application
`of orthogonal electrical potentials is overlaid with a
`?exible conductive sheet and spaced therefrom so as to
`normally prevent contact therebetween but permit
`contact when the ?exible sheet is deformed by an ob
`ject having a radius of curvature less than a speci?c
`value, wherein the improvement comprises: discrete
`insulator buttons of substantially uniform size electri
`cally separating the sheets throughout the sens0r,_the
`buttons having a height and an average spacing
`whereby the maximum radius of curvature of the object
`to which the sensor will respond is approximately equal
`to the square of the average spacing between the but
`tons divided by eight times the height of the buttons.
`4. The sensor of claim 3 wherein the insulating but
`tons are attached to the surface of the conductive
`sheet.
`5. The sensor of claim 3 wherein the buttons have a
`diameter from about 0.001 to about 0.015 in., the
`height thereof is from about 0.0005 to about 0.015 in.,
`and the average spacing between the buttons is from
`about 0.025 to about 0.075 in.
`6. The sensor of claim 3 wherein the electrodes at
`tached to the resistive sheet are a plurality of spot elec
`trodes equally spaced along each edge of the resistive
`sheet; and further comprising a plurality of discrete re
`sistors each of which are connected between adjacent
`of the spot electrodes whereby a series resistor network
`is formed along each edge of the resistive sheet.
`* * *
`=l<
`*
`
`20
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`65
`
` Exhibit 1014 Page 6