US3629774A - Progressively collapsible variable resistance element - Google Patents

Progressively collapsible variable resistance element Download PDF

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US3629774A
US3629774A US772464A US3629774DA US3629774A US 3629774 A US3629774 A US 3629774A US 772464 A US772464 A US 772464A US 3629774D A US3629774D A US 3629774DA US 3629774 A US3629774 A US 3629774A
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resistance element
coating
elastic
resistance
network
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Nelson A Crites
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Scientific Advances Inc
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Scientific Advances Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C10/00—Adjustable resistors
    • H01C10/10—Adjustable resistors adjustable by mechanical pressure or force
    • H01C10/106—Adjustable resistors adjustable by mechanical pressure or force on resistive material dispersed in an elastic material

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  • a resistance element of elastic material has at [54] PROGRESSIVELY COLLAPSIBLEVARIABLE least an interconnected portion coated with a nonfriable elec- RE I TA ELEM trically conductive material forming an electrical path that Chin" 26 Drum! changes its resistance as a function of the state of tension or 52] us. c1 338/114, compression of the resistance eme t.
  • a conductive material 117/226, 252/502, 338/99 is prepared from particulate electrical conductive material, an 511 1111.01 1101c 13/00 elastic binder and a solvent e atment of an elastic materi- 501 r1610 61 sun-611 333/2, 36, al of elaswmer foam p i t pplication of conductive materia1 produces a useful resistance element.
  • This invention relates to a resistance element and method of making a conductive material and, more particularly, this invention relates to an elastically collapsible resistance element having an electrical resistance varying with the state of tension or compression of the resistance element. This invention further relates to low-cost transducers constructed from the aforesaid resistance element.
  • a low-cost device that has been used in the latter applications includes an arm which is actuated mechanically to traverse a coil connected in an electrical circuit. The movement of the arm and the resistance of the circuit change with the amount of force applied to the arm.
  • the present invention provides a resistance element which typically comprises an elastic material having a progressively collapsible skeletal structure and a nonfriable elastic electrically conductive continuous coating adherent to at least an interconnected portion thereof, the coating having an average thickness of about 0.05 to 0.25 of the thickness of the skeletal structure, and the element filling less than about 25 percent of the volume within its outer boundary.
  • the coating comprises an elastic binder and electrically conductive particles dispersed therein to form a substantially smooth outer surface at which the conductive particles are substantially, but not completely, embedded.
  • the conductive material typically comprises about 10 to 25 percent of the volume of the coating.
  • a preferred form of progressively collapsible variable resistance element comprises a threedimensional network of interconnecting strands of elastic material integrally interconnected by nexuses at spaced points to form the skeletal outline of a multitude of polyhedrons each face of which is polygonal and common to a pair of adjacent polyhedrons, substantially all of the faces being open and free from membranous elastic material; and a nonfriable elastic coating, substantially covering the interconnecting strands and nexuses without substantially filling the open polygonal faces, which comprises an elastic binder and electrically conductive particles dispersed therein to form a substantially smooth outer surface at which the conductive particles are substantially, but not completely, embedded in the binder.
  • the average thickness of the coating is generally less than about 0.5 of the radius of the interconnecting strands and the network typically has about 10 to I00 polygonal faces per lineal inch.
  • the skeletal network is preferably formed of a polyurethane resin and the conductive particles are preferably carbon.
  • Another useful form of the progressively collapsible variable resistance element may comprise an interwoven structure of fibrous strands, a layer of elastic material substantially covering those strands and bonding them at spaced points of intersection to form a three-dimensional interconnected network substantially free of membranous material in the areas between strands, the elastic layer imparting elasticity to the structure as a whole, and a nonfriable elastic coating substantially covering the network without substantially filling the areas between strands, which comprises an elastic binder and electrically conductive particles dispersed therein to form a substantially smooth outer surface at which the conductive particles are substantially, but not completely, embedded in the binder.
  • the invention also includes a method of making a nonfriable elastic coating having conductive particles dispersed therein to form, when applied, a substantially smooth outer surface at which the conductive particles are substantially, but not completely, embedded which comprises the steps of heating the conductive particles under vacuum to remove impurities, cooling the conductive particles to a predetermined temperature insufficient to cause vaporization of a selected liquid, adding to the conductive particles, to form a paste, a liquid that does not vaporize at that temperature, adding a flowable elastic material to the paste to form a conductive composition, mixing the conductive composition to disperse the conductive particles uniformly therein, and adding a catalyst to the mixed composition to promote cross-linking of the elastic material.
  • Additional liquid may be added to the conductive composition after mixing to reduce its viscosity to a level that enables the composition to penetrate freely into substantially all of the open cellular regions of an elastic porous mass.
  • the liquid may be a solvent or an emulsifying agent.
  • a method of making a progressively collapsible variable resistance element from a substantially completely open-celled, three-dimensional network of interconnecting strands of elastic material which comprises applying to at least a portion of the outer surface of the network a flowable nonfriable conductive coating comprising an elastic binder and electrically conductive particles dispersed therein to form a substantially smooth outer surface at which the conductive particles are substantially, but not completely, embedded, spreading the coating on the network until it is evenly distributed over the outer surface thereof, centrifuging the network to remove excesscoa ting, and drying and curing the coated network to set the elastic binder.
  • the network may be saturated with a liquid before applying the coating.
  • FIG. 1 is a sectional view of a relaxed resistance element according to the invention
  • FIG. 2 is a sectional view of the resistance element of FIG. 1 in a compressed state
  • FIG. 3 is a sectional view of another resistance element according to the invention.
  • FIG. 4 is a sectional view of still another resistance element according to the invention.
  • FIG. 5 is a sectional view of yet another resistance element according to the invention.
  • FIG. 6 is a sectional view of still another resistance element according to the invention.
  • FIG. 7 is a sectional view of another resistance element according to the invention.
  • FIG. 8 is a sectional view of still another resistance element according to the invention.
  • FIG. 9 is a perspective view,of yet another resistance element according to the invention.
  • FIG. 10 is a perspective view partially in cross section of a transducer according to the invention.
  • FIG. 11 is a perspective view partially in cross section of another resistance element for the transducer of FIG. 10;
  • FIG. 12 is a sectional view of a load cell made from the transducer of FIG. 10.
  • FIG. 13 is a perspective view of a Bourdon tube made with read-out means including a transducer according to the inventron;
  • FIG. 14 is a sectional view of a temperature compensated transducer according to the invention.
  • FIG. 15 is a sectional view along the line 15l5 of FIG. 14;
  • FIG. 16 is a cross-sectional view of a high output temperature compensated transducer according to the invention.
  • FIG. 17 is a cross sectional view of another high output temperature compensated transducer according to the invention.
  • FIG. 18 is a graph of the hysteresis behavior of a transducer made from the resistance element according to the invention.
  • FIG. 19 is a graph of the sensitivity or change of resistance per unit of force applied to a variety of resistance elements made according to the invention.
  • FIG. 20 is a graph of the sensitivity or change of resistance per change of unit length for a variety of resistance elements made according to the invention.
  • FIG. 21 is a perspective view of a transducer having controlled resistance characteristics according to the invention.
  • FIG. 22 is a cross-sectional view of another transducer having controlled resistance characteristics according to the invention.
  • FIG. 23 is a photomicrograph (20X) of a section of a coated, reticulated polyurethane foam resistance element according to this invention.
  • FIG. 24 is a photomicrograph (IOOX) of a cross section of one of the interconnecting strands of the resistance element shown in FIG. 23.
  • FIG. 25 is a photomicrograph (200X) of a portion of the cross section of a strand such as shown in FIG. 24, showing the conductive coating.
  • FIG. 26 is aphotomicrograph (5,000X) taken to the surface of the conductive coating on an interconnecting strand such as shown in FIG. 25.
  • the invention includes within its scope a resistance element and method of making a conductive material wherein the resistance element includes an elastic material having a progressively collapsible structure having at least an interconnected portion thereof coated with a nonfriable electrically conductive material.
  • the conductive material forms an electrical path through the aforesaid resistance ele- 1 ment. It has been found that the use of the aforesaid resistance elements in a low-cost transducer obviates many of the difficulties attendant upon low-cost transducers heretofore in use and provides many advantages.
  • the elastic material can be made from a variety of materials and may assume many dif ferent configurations.
  • the electrically conductive coating material must be nonfriable but most importantly should be firmly adherent to the elastic material.
  • An important feature of this invention is that the composition of the conductive coating material can be tailored to the environment in which it is to be used.
  • the conductivity of the conductive coating and the degree of its influence on the elasticity of the elastic material are selected with reference to the sensitivity of the system of which it is to comprise a component member. For example, where high sensitivity is required, the conductivity is relatively low and the coating exerts little or no influence on the elastic behavior of the elastic material.
  • FIG. I a cross section of an embodiment of a resistance element selected for purposes of illustration is in a relaxed position.
  • the element comprises a cellular foam having the cell walls 13 of the interconnected cells 12 bonded with a conductive coating 15.
  • the structure of FIG. 1 is elastically compressed in FIG. 2 causing cell walls 13 of the relaxed structure to collapse so that the space in each cell 12 decreases as well as the ratio of void to solid space in the cellular element. It will be obvious that this decrease of void space will occur progressively with compression of the cellular element.
  • the closer proximity of areas of conductive coating 15 upon compression decreases the length of the current path and thus the electrical resistivi- I ty.
  • the conductive coating 15 yields with the movement of cell walls 13 as a result of being nonfriable and adherent. It is not necessary that coating 15 be as elastic as the material of the cell walls 13 because a firm bond'of coating 15 to elastic cell walls 13 insures elastic movement of the entire structure.
  • interconnected cells 12 Upon relaxationpf the foam of FIG. 2, interconnected cells 12 will open progressively and the electrical resistance will increase until it reaches the relaxed position of FIG. I. Extension or stretching of the relaxed structure of FIG. 1 will cause a further increase of resistance.
  • the resistance element is suitable for measurement of either tensile or compressive forces.
  • an elastic material comprises a porous body of small irregularly shaped particles 26 held together at points or small contact surfaces 28.
  • each particle 26 may have an interconnected cellular network as exemplified in the photomicrograph of FIG. 23.
  • a conductive element is prepared in one method by first bonding the contact points by preliminary coating of the particles with a bonding material and subsequent compaction to the desired level of porosity. The degree of porosity depends on the size required for the voids 22. The bonded porous mass is then impregnated with a conductive coating material 25 which bonds to the free surfaces defining void spaces 22.
  • the bonding material used for preliminary coating of the particles can also serve as the conductive coating where satisfactory bonding can be achieved at the contact points with the conductive coating.
  • conductive coating 25 is brought into tighter contact over larger areas by progressive closing of void spaces 22 to cause a change of electrical resistance.
  • another porous body comprises a plurality of hollow spheres 36 bonded at their contact points 38 and defining the void spaces 32, the spheres having thereon a conductive coating 35.
  • the resistance element of FIG. 4 can comprise solid spheres of resilient material unitized in a porous mass such as the body of irregular particles of FIG. 3.
  • the body can comprise a plurality of spheres or irregular shapes of sponge rubber bonded at their contact points.
  • cylindrical shapes or ellipsoids, prolate spheroids, etc., randomly disposed in a porous mass and bonded at their contact points provide a suitable material.
  • intermingled fibers, flakes or shells'46 form a strong elastic fibrous unit containing therein void spaces 42.
  • the fibers or flakes 46 are interlocked along their length either by chemical combination, by means of secondary forces, or by mechanical entanglements.
  • a mass of randomly oriented steel fibers can be interlocked by mechanical entanglement.
  • chemical combination is used to interlock the fibers.
  • numerous other fiber materials are satisfactory. For example, hogs hair coated with a latex solution can provide an elastic material having excellent resilience.
  • a typical bonded junction of fibrous strands as in FIG. 5 may appear in cross section as in the photomicrograph of FIG. 24.
  • a metal comprises a plurality of overlapping portions of alternate flat layers 66 and corrugated layers 67 wherein the walls of the corrugated layers form cells 62 having a cross-sectional area increasing with distance from the point of contact 68 of corrugated layers 67 and fiat layers 66.
  • the angle defined at the intersection of fiat layers 66 with corrugated layers 67 should be relatively low to insure a progressive closing or opening of cells 62 upon compression of extension.
  • a modification of FIG. 6 is a metal foil having a plurality of overlapping portions 74 forming stacked cells 72 having a depth increasing with distance from the point of contact 71 with its adjacent cell. A portion of the metal inside of cells 72 is embossed so that ease of contact is assured upon progressive closing or opening of cells 72 upon compression or extension of the elastic body.
  • the elastic body can merely comprise a series of stacked embossed plates bonded at the point of contact with their adjacent plates.
  • superimposed plates 76 having embossed portions 77 are arranged so that the embossed portion 77 contacts a flat portion on a lower adjacent plate at contact point 78.
  • the space between the embossed portion and the flat portion of an upper adjacent plate forms cells 79.
  • the stacked plates are not continuous in FIG. 8, only the underside of the plates is coated with conductive material. The current path changes when the points of contact progressively enlarge upon compression of the body.
  • Another resistance element similar to that of FIG. 8 can be made by using alternate corrugated and fiat plates rather than the continuous metal foil as described in FIG. 6.
  • FIG. 8 can be made continuous by interconnecting the plates as shown in FIGS. 6 and 7.
  • a first insulating coating which may be formed merely by oxidation of the metal is covered with a firmly adherent conductive coating.
  • an interconnected collapsible structure has a plurality of cellular units that collapse or extend progressively in relation to the applied force.
  • the use of a plurality of cells, each opening or closing progressively with compression or extension, provides excellent reliability in comparison to a configuration where, say, a single larger collapsible cell is used.
  • the effect provided in the multicellular structures can be provided in a structure of the latter type wherein each portion having the ability to open or close progressively in relation to applied force runs the full length of the resistance element.
  • a plurality of springs 52 of varying pitch are placed in spaced relation to one another.
  • Each coil 56 of a spring 52 is spaced from its neighboring coil by a distance that decreases from one end of the spring to the other end.
  • the space defined between coil 56A and 56B is greater than the space defined between coil 56B and 56C.
  • FIGS. 5, 6, 7, 8, and 9 are metals
  • an adherent conductive coating having a high resistance relative to that of the metal is used. In this way, changes of dimension of the elastic material that affect the resistance of the resistance element are readily apparent.
  • the conductive coating can form a current path through the structure, a first insulating coating is applied to the metal. The conductive coating is then applied over the first insulating coating.
  • electrically conductive material can be incorporated in the nonconductor. In most cases, the amount of electrically conductive material will be small so as to not adversely affect the elastic properties of the nonconductor. In either event, an adherent conductive coating must be applied to the nonconductor.
  • elastomer foams of silicone rubber known as Silastic R'IV Silicone Rubber (trade name of Dow Corning Corporation) and RTV 7 Silicone Rubber (trade name of General Electric Company) are satisfactory.
  • the foremost requirement for the nonconducting foams is that the cells should be interconnected so that an electrical path is available upon application of the conductive coating.
  • a foam of controlled cell size is easily prepared by mixing appropriate quantities of elastomer and sugar or salt crystals or other soluble crystals of predetermined uniform size. When the rubber sets, the crystalline material is leached away to leave a foam body.
  • a heat decomposable material can also be used to locate the ultimate cell sites in the foam body. Manual working of the foam ruptures sufficient cell walls to provide the interconnection needed for an electrical path.
  • a useful body of elastomer foam comprises a skeleton foam of a first resilient material uniformly coated and impregnated with a second resilient material.
  • the composite foam thus formed is used where a foam material is needed for its properties such as resilience or resistance to chemical attack but cannot be obtained commercially in a uniform cell size.
  • the properties of silicone rubber render it desirable for a foam material.
  • a suitable composite foam is available from a commercial polyurethane foam of uniformcell size having the pores thereof coated with three to four times its weight of silicone rubber.
  • the composite has better resiliency and resistance to chemical attack than a polyurethane foam alone and a more uniform cell size than a silicone foam alone.
  • polyurethane foam is impregnated with a solution of silicone-acetic anhydride-xylene mixture.
  • the xylene is released along with the acetic anhydride and the silicone rubber vulcanizes in place around the polyurethane skeleton.
  • the conductive coating of this invention must be: (1) capable of being adherent to the elastic material or forming a firm bond therewith; (2) nonfriable; and (3) electrically conductive.
  • the elastic material is ordinarily dipped in a solution of the conductive coating. Where demanded by the shape of the elastic material, impregnation is done by capillary action and can be aided by application of a vacuum.
  • a satisfactory conductive coating includes an elastomer combined with a particulate electrical conductor. A variety of elastomers and electrical conductors can be used.
  • elastomers would include RTV (room temperature vulcanizable) silicone rubber, natural rubber latex, polyurethane rubber, etc.
  • RTV silicone rubber is Clear Seal (trade name of General Electric Company).
  • Electrically conductive materials include carbon, graphitized or partially graphitized carbon, silver, gold, copper, tungsten, aluminum, and various metals and alloys used alone or in combination with one another.
  • An example of a satisfactory electrically conductive material of carbon is Conductex SC (trade name of Columbian Carbon Corporation).
  • Conductex SC is a carbon black which has a mean particle diameterof 170 A. Extremely fine particles such as these are desirable in that they allow a more uniform conducting surface to be obtained.
  • the outer surface of the coating is substantially smooth. There are no brittle conducting fiber ends protruding for some distance from the surface which can break off during compression or expansion of the resistance structure. Also, the conducting particles are not merely bonded onto the surface of the coating where they can abrade off during deformation. in the present invention the conducting particles which are generally very fine, are substantially, but not completely, embedded in the coating surfaces such that they will not break or abrade off. This allows resistance elements according to this invention to be used for prolonged periods of time without significant changes in resistance values or in linearity.
  • the amount of electrically conductive material used in the conductive coating or its loading and the amount of coating applied to the elastic body will be dictated by the electrical characteristics and mechanical properties desired in the final product.
  • electrical characteristics and mechanical properties it is meant to refer to the sensitivity of the resistance elementor the change of resistance per unit length or force, and the hysteresis behavior of the resistance element, as well as the actual resistance of the resistance element in its relaxed position.
  • electrical characteristics and mechanical properties it is meant to refer to the sensitivity of the resistance elementor the change of resistance per unit length or force, and the hysteresis behavior of the resistance element, as well as the actual resistance of the resistance element in its relaxed position.
  • the resistance element is being used as a transducer to measure relatively high pressure, it will be desired to use a relatively high modulus element. Where pressures are low, a low modulus element having a broad range of resistance is desired to pick up slight changes in the surroundings.
  • the resistance of the conductive coating is readily controlled by the amount used as well as by its loading.
  • the modulus of the elastic material can be influenced by the amount of coating used.
  • the effect of the conductive coating on the modulus of the elastic material depends to some extent on the nature of the elastic material. The effect is more pronounced in the case of a low modulus material (e.g., elastomer foam) than it is in the case of a high modulus material (e.g., metal spring).
  • a low modulus material e.g., elastomer foam
  • a high modulus material e.g., metal spring
  • One preferred method of making a conductive coating comprises forming a dispersion of particulate electrically conductive material in a liquid containing an elastic material. Conductive coating made in this manner are well suited for resistance elements according to the invention.
  • the preferred method of producing an elastic, nonfriable conductive coating includes the steps of:
  • the final coating composition has a thick, pasty consistency and is therefore difficult to work into the inner cellular regions of an elastic porous mass.
  • it is desirable to add more liquid to the composition preferably the same liquid as is used to form the conductive particle paste.
  • This liquid is preferably added after the mixing step wherein the particles are uniformly distributed and serves to reduce the viscosity of the final coating, thereby enabling the coating to penetrate freely into substantially all of the open cellular regions.
  • the conductive particles constitute about 10 to 25 percent of the volume of the coating. When carbon particles are used, they may constitute about 20 to 50 percent of the coating by weight. It has been found that where the coating contains a very small amount of conductive particles, it will not produce the required resistance characteristics, and that where it contains too many particles, the elasticity of the coating is decreased to an extent which will undesirably affect the element as a whole. Therefore, the amount of conductive particles in the coating (also referred to as loading) must be within certain prescribed ranges to be useful.
  • the liquid carrier for the elastic material can be either a solvent or an emulsifying agent.
  • a solvent such as naphtha, xylene or other aromatic hydrocarbon, is employed.
  • the total amount of solvent used is dictated by the amount of coating desired for the particular application. Increased amounts of solvent cause greater dilution or lesser amounts of coating after the solvent is driven off. The solvent is driven off after the coating is applied to the elastic body by the application of moderate amounts of heat.
  • the elastic structure is coated merely by dipping in the conductive coating.
  • the elastic structure consists of a substantially completely open-celled, threedimensional network of interconnecting strands, such as a reticulated elastomer foam, it is often .difficult to obtain complete penetration of the coating and at the same time prevent clogging of the pores.
  • a flowable nonfriable conductive coating comprising an elastic binder and electrically conductive particles dispersed therein to form a substantially smooth outer surface at which said conductive particles are substantially, but not completely, embedded;
  • the centrifuging step is important in that it removes any excess coating material that may be clogging the pores of the structure and also removes excess coating material of the interconnecting strands themselves such that only a thin layer of coating is left on each strand. It has been found that the coating must have an average thickness of about 0.05 to 0.25 of the thickness of the skeletal structure and that element comprising the skeletal structure with its adherent coating must fill less than about 25 percent of the volume within its (the element) outer boundary. By adjusting the duration of the centrifuging step, the thickness of the coating may be controlled within the desired limits.
  • the elastic material comprises an elastomer such as a foam of silicone rubber
  • a solvent such as naphtha, xylene or other aromatic hydrocarbon
  • the pretreatment a portion of the solvent used to carry the conductive coating is eliminated for use as a carrier and substituted in the pretreatment operation.
  • the elastomer is allowed to soak in the solvent until it is saturated.
  • the pretreatment is observed to 'cause swelling of the foam. The larger pores thus formed allow easier penetration of the foam upon impregnation with conductive material immediately following the solvent pretreatment.
  • the solvent pretreatment is found to have advantages with regard to the electrical characteristics of the resistance element as well as its mechanical properties.
  • the former advantage finds application in the production of resistance elements of elastomer foam whereas the latter application has even wider application.
  • the elimination of a portion of the solvent from the conductive coating results in a mixture of pasty consistency. Because of the decreased solvent requirement, greater amounts of coating can be used to provide a higher effective carbon content than previously available without pretreatment. Previously, the need for high solvent limited the amount of coating that could be used thereby requiring increased loading of conductive material in the coating to provide higher conductivity. It will be apparent that with the solvent pretreatment, higher conductivity coatings can be made with reduced amounts of conductive material.
  • the benefits of pretreatment on mechanical properties relates to the interaction of the conductive coating with the elastomer wall.
  • the advantage derived renders the pretreatment suitable for preparing resistance elements from a composite of solid elastomer and conductive coating as well as from an elastomer foam.
  • the solvent used for pretreatment apparently does not evaporate until after vulcanization of the elastomer of the conductive coating thereby minimizing the possibility of microcracking.
  • the reduced amount of solvent needed to carry the conductive coating also reduces the possibility of microcracking from this source.
  • Another surprising advantage relating to mechanical characteristics is found to result upon evaporation of the absorbed solvent.
  • the elastomer body shrinks to compress the coating and in effect prestresses the coating.
  • the latter advantage makes the pretreatment process especially useful for resistance elements comprising a solid elastic substrate coated with a conductive coating wherein expansion or contraction of the composite causes the resistance of the conductive coating to change proportionally.
  • a transducer is provided by affixing electrical leads to the top and bottom metal portions and including the resistance element in a suitable electrical circuit.
  • an elastic foam body has an interconnected cellular portion 82 coated with a conductive coating 85. While an elastic material of nonconductive foam is shown in FIG. 10, it is not meant to be limited thereto. Any of the elastic materials of FIGS. 3 to 5 or FIG. 9 may be used.
  • Contacts 89 are affixed to the longitudinal ends of foam 80 by means of an electrically conductive cement 88.
  • a satisfactory cement comprises equal proportions by volume of a solvent release cement having the ability to shrink upon curing and a mixture of silver flake and silver powder.
  • Wolfson et al. (US. Pat. No. 2,774,747) described a typical conductive cement.
  • Leads affixed to contacts 89 connect transducer 84 in an electrical circuit comprising a power source and electrical readout device.
  • FIGS. 1 and 2 when foam 80 changes dimension by reason of physical force applied thereto, there is a corresponding change in the current path or electrical resistance measured by the electrical readout device.
  • an elastic material can be used alone as in FIG. 10, the use of a solid elastic material such as liver rubber in combination therewith relieves a portion of the stress.
  • foam 80 of FIG. can be impregnated to a limited depth only so that only a portion of the foam is axially traversed by conductive material.
  • the axial core 96 of foam 90 having a conductive coating on the interconnected cell walls thereof receives a solid elastic material 97.
  • Contacts (not shown) are affixed to ends of the composite body as described in connection with FIG. 10.
  • the solid elastic material 97 of FIG. 11 may comprise live rubber or any other highly resilient material such as a fiberglass spring or metal spring insulated from the conductive coating.
  • solid elastic material may be a coaxial portion such as a sleeve surrounding the foam body.
  • the solid elastic material may be combined with any of the coated elastic materials such as those illustrated in FIGS. 1 through 9.
  • a load cell 110 comprises a transducer 104 inside of a bellows 108 having the ability to deform elastically uniformly in a longitudinal direction with applied pressure.
  • the contacts 106 of transducer 104 are insulated from bellows 108 by insulating discs 109.
  • Leads 101 from a power source carry current to the transducer and are insulated from bellows 108.
  • the transducer is left unaffected by the presence of the fluid. Further, the deformation of the transducer can be controlled by the elastic properties of the bellows.
  • FIG. 12 provides a method of controlling the modulus of the elastic material in addition to the previously described method of adjusting the amount of conductive coating.
  • a further application for the transducer of this invention includes the Bourdon tube 120 of FIG. 13 wherein a transducer 124 is grasped between the opposing faces 116 and 118 of Bourdon tube 120. Insulating plates 125 serve to insulate the contact caps 127 from faces 116 and 118. Transducer 124 is connected to a power source (not shown) by leads I21. Fluid enters faces I16 and 114 and flows to closed face 118 whereby pressure in tube 120 causes face 118 to move outwardly to release force on'transducer 124 in an amount proportional to the fluid pressure. In turn, force released from the transducer causes the length of the current path flowing in the transducer circuit to change.
  • the mechanical arrangement normally used in the Bourdon tube to transmit the changes of tube geometry to a pointer or readout device can be included with the arrangement of FIG. 13. In this manner, two types of readout are provided.
  • the transducer according to this invention shows remarkably little change in properties when subjected to varying temperatures. However, where close accuracy is needed, temperature compensation is usually desired.
  • the outer resistance elements 135 and 136 surround the shorter inner resistance elements 131 and 132.
  • the upper end of inner resistance elements 131 and 132 and outer resistance elements 135 and 136 are affixed to an insulating plate 138.
  • Insulating plate 139 is affixed to the lower ends of outer resistance elements 135 and 136.
  • Leads 141 from a power source (not shown) are attached to resistance elements 135 and 136.
  • Outer resistance elements 135 and 136 are responsive to pressure whereas inner resistance elements 131 and 132 are not.
  • Leads 142 through 146 interconnect the resistance elements so that each element comprises one arm of a Wheatstone Bridge circuit.
  • Each of the inner elements 131 and 132 is connected to one of the outer elements and 136 so that an inner element and an outer element comprise alternate arms in the bridge circuit. Because the voltage drop across them is equal to the applied voltage, their outputs are added and the output is doubled.
  • wires can be used to interconnect the resistance elements in the bridge circuit, some leads can be printed on the inner face of the contacts by conventional techniques. To insure maximum output on the bridge circuit, the resistance of all the resistance elements should be equal. In other words, the fixed resistance of the elements not responsive to pressure should be equal to the normal resistance of the elements responsive to pressure.
  • normal resistance it is meant the resistance of the responsive elements prior to being placed in the environment in which the transducer operates. This is done according to the invention by varying the composition and amount of conductive coating applied to the resistance element.
  • the inner elements do not have to comprise resistance elements according to the invention so long as their resistance is equal to the normal resistance of the outer elements and they respond to temperature in the same manner as the outer elements.
  • a load cell can be made by including the temperature-compensated transducer of FIGS. 14 and 15 within the bellows of FIG. 12.
  • a temperature-compensated transducer has four times the output of a transducer comprising one element alone.
  • the transducer comprises the upper resistance elements 161 and 162 and the lower resistance elements 168 and '169 affixed to the end caps 159 and 171, respectively, at one end and affixed at their opposing ends to an insulating plate 165 having a pressure applying disc 166 affixed to its rim.
  • the transducer assembly is disposed inside of a bellows assembly 179 and separated therefrom at the longitudinal ends by the insulating discs 157 and 173.
  • pressure applying disc 166 is affixed to the bellows assembly 179 to define an upper bellows portion 155 and lower bellows portion 177.
  • the tabs 153 are affixed to the upper and lower faces of bellows 179.
  • the resistance elements are connected by electrical leads 175 so that each resistance element comprises one arm of a Wheatstone Bridge arranged with upper and lower resistance elements as alternate anns.
  • spaced rods are run through the openings in tabs 153 so that the position of the transducer is fixed and pressure of the surrounding environment is transmitted solely to pressure applying disc 166.
  • Leads from a power source (not shown) are connected to end caps 159 and 171.
  • the lower bellows portion 177 and lower resistance elements 168 and 169 are compressed while the upper bellows portion 155 and upper elements 161 and 162 are placed in tension.
  • the normal resistance of the resistance elements of FIG. 16 is about equal.
  • a modification of the transducer of FIG. 16 comprises the transducer assembly enclosed within a rigid container 198 and insulated therefrom by the insulating plates 191 and 199.
  • a rod 192 extends through an opening in the top of the rigid container 198 and is affixed at its base to insulator plate 193.
  • Pressure responsive means 189 are provided on the portion of rod 192 outside of rigid container 198.
  • the transducer assembly 195 responds in the manner described for FIG. 16.
  • the resistance elements of FIGs. 16 and 17 that are stressed in tension may initially be in the relaxed state or compressed (prestressed). The latter alternative is useful where the resistance material has a low tensile strength.
  • the most useful resistance element of FIGS. 1 through 9 for the transducers of FIGS. 12 through 17 will be determined by the properties sought to be measured and the accuracy desired.
  • the resistance elements were placed in a warm oven until the solvent was driven off. Electrically conductive cement was used to affix brass contacts having a diameter of about five-eighths inch and a thickness of about 0.050inch to each end of the resistance element. Leads were affixed to the electrodes so as to complete an electrical circuit including a power source and electrical readout device. Load was applied to each transducer and the electrical resistance measured at various deflections. Upon full compression of the resistance element, load was gradually released in small increments so that deflection and resistance could be recorded. The graph of FIG. 18 shows the hysteresis behavior of the three transducers. Excellent reliability is shown for the numerous ranges of resistance that are covered.
  • EXAMPLE 2 The useful resistance ranges of resistance elements made in the manner of the transducers of example I silicone foams of two different densities were determined in relation to the conductivity of the coating and amount of conductive coating used. Measurements of electrical resistance were made in the relaxed state and in the fully compressed state. The tabulation below compares the resistance ranges with the amount and conductivity of the conductive coating.
  • ZOO-Density of Foam l0.9 lit/ft.
  • 300-Demity of Fonrn 8.5 lbJft.
  • EXAMPLE 3 Transducers were made in the manner described for example land the relationship of force to change of resistance per unit of force applied and change of resistance per change of unit length were studied for various amounts and conductivities of conductive coatings. In this way, the effect of the latter variables on sensitivity could be studied. Referring to FlGs. l9 and 20, the sensitivity of the resistance elements varies within a wide range depending on the amount and type of conductive coating that is used. This allows conductive elements to be tailored for specific environments.
  • EXAMPLE 4 The useful resistance ranges of resistance elements were studied as a function of the manner of applying a conductive coating. Resistance elements were made from an elastic material of silicone rubber foam having a density of 8.5 lb./ft. and a length of three-eighths inch and a diameter of 1% inch. Conductive coating for sample 101 was prepared by mixing xylene with silicone rubber (GE Clear Seal) and particular carbon (Conductex SC Beads) and ball milling for Sminutes. Immediately following ball milling, the resistance element was prepared by dipping the foam body in the coating solution.
  • silicone rubber GE Clear Seal
  • particular carbon Conductex SC Beads
  • sample 103 percent of xylene that was used for the conductive coating of sample 101 was used to impregnate the foam body prior to dipping it in a coating solution containing 80 percent less xylene than was used for the conductive coating of sample 101.
  • Transducers were prepared in the manner described for example land measurements of electrical resistance made in the relaxed state and with an applied force of 50 grams.
  • sample 103 was cycled several times with no change in the resistance from that shown above. The ball milling procedure is also shown to provide higher conductivity as evidenced by comparing sample 303 of example 2 with sample 101.
  • a transducer having a variable modulus so that the electrical resistance characteristics of the transducer upon deformation can be closely controlled. This allows adjustment of the sensitivity of the transducer within various deformation ranges.
  • a pair of stacked verticalresistance elements 212 and 214 to form the resistance element 216 are provided between the electrical contacts 219 affixed to each of the longitudinal ends of the resistance element 216.
  • the elements 212 and 214 are affixed to one another and to the contacts 219 by means of electrically cosductive cement 218 Where resistance elements 212.
  • the lower modulus material collapses rapidly upon initial compression of the transducers to cause an immediate change of resistance.
  • the element of higher modulus collapses more slowly and causes a further change of resistance with deformation after the lower modulus element has ceased to be effective.
  • a transducer 225 having controlled resistance change with deformation comprises a resistance element 227 of elastomer foam between electrical contacts 237 forming a central opening 229 provided with an insulated spring 231 and a resilient stop 233.
  • Initial deformation of the transducer 225 causes a change of resistance dictated by the characteristics of the resistance element 227.
  • the upper contact 237 strikes spring 231 whereby it controls additional deformation of the resistance element 227.
  • the stop controls further deformation.
  • the transducer can be subjected to higher deformation thereby extending its useful pressure operating range.
  • FIGS. 23 to 26 A preferred embodiment of the variable resistance element according to the present invention is shown in FIGS. 23 to 26.
  • This embodiment comprises a commercial polyurethane foam having a first coating of silicone rubber which is in turn coated with an elastic electrically conductive material.
  • FIGS. 23 to 26 are photomicrographs of increasing magnification which show in greater detail the structure of the element.
  • FIG. 23 shows the cellular structure of a reticulated polyurethane foam coated with a conductive coating according to this invention. It is clear from this photomicrograph that the coated foam is a substantially open celled structure and that the greater portion of its volume is void space.
  • FIG. 24 shows a cross section of one of the interconnecting strands of the coated structure. The dark triangular portion the center of the strand is the reticulated polyurethane foam structure. Reticulated or dewindowed foam structures such as these are commercially available from Scott Paper Company and are more fully described in U.S. Pat. No. 3,l7l,820, Volz. The light portion immediately surrounding the triangular polyurethane core is the first coating of silicone rubber. Coating the polyurethane core with silicone rubber in this manner greatly improves the mechanical properties of the cellular structure.
  • the first silicone coating is preferably dried and cured before applying the conductive coating.
  • FIG. 25 shows that the outer surface of the coating is substantially smooth and free from protruding particles on fiber ends. It is also apparent from FIG. 25 that the carbon particles are uniformly distributed, over the surface of the coating.
  • FIG. 26 is photomicrograph of a portion of the surface of the coating taken normal to the surface and magnified to 5,000 X.
  • the white fibers in FIGS. 26 are a filler material in the silicone rubber elastic binder.
  • the carbon particles are still too small to be visible but they are substantially embedded in the silicone rubber in the evenly distributed dark areas to the photo. Resistance elements such as the one shown in FIGS.
  • the preferred reticulated foam structures comprise a threedimensional network of interconnecting strands of elastic material integrally interconnected by nexuses at spaced points to form a skeletal outline of a multitude of polyhedrons each face of which is polygonal and common to a pair of adjacent polyhedrons, substantially all of the faces being open and free from membranous elastic material. Structures having [0 to faces per lineal inch (commonly referred to as pores per lineal inch) are preferable.
  • the reticulated foam structure may be made of silicone rubber, thus eliminating the intermediate silicone rubber layer. More than one intermediate layer may be used where desirable.
  • Resistance elements as illustrated by the invention characterized by an elastic material defining a collapsible structure having at least an interconnected portion bonded with a conductive coating have many uses and advantages.
  • the uses of the resistance element include measurements of torsion, strain, and angular displacement as well as low-level acoustical pickups.
  • Transducers according to the invention find uses including the measurement of force, "pressure and torsion.
  • Temperature-compensated transducers find use for measurements above room temperature where the combined factors of low cost and accuracy are relevant.
  • One advantage of this invention is that a resistance element is provided having an electrical resistivity varying in a simple functional relation with the state of tension or compression of the resistance element.
  • Another advantage of this invention is that a low-cost resistance element is provided having an electrical resistivity and sensitivity tailored to its environment and providing a reliable variation of electrical resistivity with continued application of tension or compression to the resistance element.
  • Still another advantage of this invention is that a low-cost transducer is provided having a high output.
  • a resistance element comprising an elastic material having a progressively collapsible solvent-impregnated and swollen then dried and unswollen skeletal structure and a nonfriable elastic electrically conductive continuous coating adherent to at least an interconnected portion of said progressively collapsible structure,
  • said coating having an average thickness of about 0.05 to 0.25 of the thickness of said skeletal structure
  • said element filling less than about 25 percent of the volume within its outer boundary
  • said coating comprising an elastic binder and electrically conductive particles dispersed therein and having been applied to the structure in its solvent-swollen condition and prestressed by the subsequent drying and shrinking to form a substantially smooth outer surface at which said conductive particles are substantially, but not completely, embedded.
  • a progressively collapsible variable resistance element comprising a three-dimensional network of interconnecting strands of solvent-impregnated and swollen then dried and unswollen elastic material integrally interconnected by nexuses at spaced points to form a multitude of reticulated cells substantially all faces of which are open and free from membranous elastic material;
  • a nonfriable elastic coating substantially covering said interconnecting strands and nexuses without substantially filling said open faces, comprising an elastic binder and electrically conductive particles dispersed therein and having been applied to the network in its solvent-swollen condition and prestressed by the subsequent drying and shrinking to form a substantially smooth outer surface at which said conductive particles are substantially, but not completely, embedded in said binder.
  • a resistance element as in claim 7, comprising also an intermediate layer of elastic material between the skeletal network and said coating.
  • a progressively collapsiblevariable resistance element comprising:
  • a layer of elastic material substantially covering said strands and bonding them at spaced points of intersection to form a three-dimensional interconnected solvent-impregnated and swollen then dried and unswollen network substantially free of membranous material in the areas between strands, said elastic layer imparting elasticity to the structure as a whole; and t a nonfriable elastic coating substantially covering said network without substantially filling said areas between strands comprising an elastic binder and electrically conductive particles dispersed therein and having been applied to the network in its solvent-swollen condition and prestressed by the subsequent drying and shrinking to form a substantially smooth outer surface at which said conductive particles are substantially, but not completely, embedded in said binder.

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  • Chemical & Material Sciences (AREA)
  • Dispersion Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Conductive Materials (AREA)
  • Measuring Fluid Pressure (AREA)
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Cited By (41)

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US3787718A (en) * 1972-08-08 1974-01-22 Sondell Res Deve Co Spherical electronic components
US3800112A (en) * 1972-03-23 1974-03-26 Essex International Inc Push-pull switch having self-biasing elastomeric material contacts with discrete conductive particles dispersed therein
US3836900A (en) * 1973-01-26 1974-09-17 Fleet Electronics Ltd Recording or alarm devices
US3843950A (en) * 1971-07-07 1974-10-22 Schladitz Whiskers Ag Porous electric heating element
US3918020A (en) * 1974-10-24 1975-11-04 Essex International Inc Multi-stage switching apparatus
US3936170A (en) * 1972-08-01 1976-02-03 Minolta Camera Kabushiki Kaisha Elastic electroconductive product
US3992945A (en) * 1975-06-05 1976-11-23 American Chain & Cable Company, Inc. Bourdon pressure gauge having direct-coupled electronic and visual readout
US4034265A (en) * 1973-06-18 1977-07-05 Essex International, Inc. Electric motor protector
US4054540A (en) * 1973-02-26 1977-10-18 Dynacon Industries, Inc. Pressure sensitive resistance and process of making same
US4076652A (en) * 1976-05-24 1978-02-28 E. I. Du Pont De Nemours And Company Elastic resistor compositions containing metallic-conductive particles and conductive lubricant particles
DE2644608A1 (de) * 1976-10-02 1978-05-24 Sick Optik Elektronik Erwin Sicherheitseinrichtung
US4120828A (en) * 1972-05-07 1978-10-17 Dynacon Industries, Inc. Pressure sensitive resistance and process of making same
US4203088A (en) * 1977-12-15 1980-05-13 Shin-Etsu Polymer Co., Ltd. Pressure-sensitive multiple resistor elements
US4279188A (en) * 1979-09-21 1981-07-21 Scott Robert D Acoustic coupling free electric drum
US4322983A (en) * 1979-02-02 1982-04-06 Shin-Etsu Polymer Co., Ltd. Method for generating electric signals and a push-button switch means therefor
US4347505A (en) * 1979-01-29 1982-08-31 Antroy Enterprises, Inc. Device for controlling a circuit
US4441097A (en) * 1979-01-29 1984-04-03 Antroy Enterprises, Inc. Device for controlling a circuit
EP0236222A1 (fr) * 1986-02-26 1987-09-09 Commissariat A L'energie Atomique Matériau piézorésistif utilisable pour la réalisation de sondes piézorésistives et procédé de fabrication de ce matériau
US4837548A (en) * 1987-02-05 1989-06-06 Leda Logarithmic Electrical Devices For Automation S.R.L Electric resistor designed for use as an electric conducting element in an electric circuit, and relative manufacturing process
US4900588A (en) * 1986-11-11 1990-02-13 Sharp Kabushiki Kaisha Method for the production of a carbon electrode
US4906192A (en) * 1986-12-18 1990-03-06 Smithard Michael A Electronic computerized simulator apparatus
US5305644A (en) * 1989-03-14 1994-04-26 Ercon, Inc. Force sensor
US5510783A (en) * 1992-07-13 1996-04-23 Interlink Electronics, Inc. Adaptive keypad
US5536568A (en) * 1991-03-12 1996-07-16 Inabagomu Co., Ltd. Variable-resistance conductive elastomer
WO1997018754A1 (en) * 1995-11-20 1997-05-29 Postur Phonic Technologies, Inc. Bio feedback sensor system
US6107612A (en) * 1998-01-26 2000-08-22 Martinex R & D Inc. Heating device and method
EP1020544A3 (en) * 1999-01-15 2001-09-19 Malat Division, Israel Aircraft Industries Ltd. Reactor for electrolytic reduction of CR+6
US6646540B1 (en) * 1999-06-22 2003-11-11 Peratech Limited Conductive structures
US20040207506A1 (en) * 2001-02-08 2004-10-21 Bruce Bower Current control device
US20050128047A1 (en) * 2003-03-25 2005-06-16 Tomoyasu Watanabe Pressure-sensitive resistor and pressure-sensitive sensor using the same
US7186356B2 (en) 2001-06-07 2007-03-06 Peratech Ltd. Analytical device
US20080314619A1 (en) * 2007-06-22 2008-12-25 Samsung Electro-Mechancs Co., Ltd. Conductive paste, printed circuit board, and manufacturing method thereof
US20100130889A1 (en) * 2007-01-24 2010-05-27 Convatec Technologies Inc. Elastomeric particle having an electrically conducting surface, a pressure sensor comprising said particles, a method for producing said sensor and a sensor system comprising said sensors
US20150268087A1 (en) * 2014-03-24 2015-09-24 Deringer-Ney, Inc. Apparatuses and methods for fuel level sensing
US20150340135A1 (en) * 2013-05-21 2015-11-26 Boe Technology Group Co., Ltd. Variable resistance and manufacturing method thereof
US9488515B2 (en) 2014-03-24 2016-11-08 Deringer-Ney, Inc. Apparatuses and methods for fuel level sensing
US20170092249A1 (en) * 2014-05-19 2017-03-30 Skoogmusic Ltd Control apparatus
US20170089782A1 (en) * 2014-06-18 2017-03-30 Stbl Medical Research Ag Strain gauge device and equipment with such strain gauge devices
EP3292812A1 (en) * 2016-09-12 2018-03-14 Heraeus Deutschland GmbH & Co. KG Piezoresistive material
WO2023027640A3 (en) * 2021-08-26 2023-04-27 Nanyang Technological University Binder-free stretchable interconnect
US20250004075A1 (en) * 2021-07-06 2025-01-02 Koninklijke Philips N.V. Electrical connection for use in cryogenic applications

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DE2946402A1 (de) * 1979-11-16 1981-05-21 Siemens AG, 1000 Berlin und 8000 München Verfahren und vorrichtung zur langzeitueberwachung gasfoermiger schadstoffemissionen und -immissionen, insbesondere in luft
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Cited By (53)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3843950A (en) * 1971-07-07 1974-10-22 Schladitz Whiskers Ag Porous electric heating element
US3800112A (en) * 1972-03-23 1974-03-26 Essex International Inc Push-pull switch having self-biasing elastomeric material contacts with discrete conductive particles dispersed therein
US4120828A (en) * 1972-05-07 1978-10-17 Dynacon Industries, Inc. Pressure sensitive resistance and process of making same
US3936170A (en) * 1972-08-01 1976-02-03 Minolta Camera Kabushiki Kaisha Elastic electroconductive product
US3787718A (en) * 1972-08-08 1974-01-22 Sondell Res Deve Co Spherical electronic components
US3836900A (en) * 1973-01-26 1974-09-17 Fleet Electronics Ltd Recording or alarm devices
US4054540A (en) * 1973-02-26 1977-10-18 Dynacon Industries, Inc. Pressure sensitive resistance and process of making same
US4034265A (en) * 1973-06-18 1977-07-05 Essex International, Inc. Electric motor protector
US3918020A (en) * 1974-10-24 1975-11-04 Essex International Inc Multi-stage switching apparatus
US3992945A (en) * 1975-06-05 1976-11-23 American Chain & Cable Company, Inc. Bourdon pressure gauge having direct-coupled electronic and visual readout
US4076652A (en) * 1976-05-24 1978-02-28 E. I. Du Pont De Nemours And Company Elastic resistor compositions containing metallic-conductive particles and conductive lubricant particles
DE2644608A1 (de) * 1976-10-02 1978-05-24 Sick Optik Elektronik Erwin Sicherheitseinrichtung
US4203088A (en) * 1977-12-15 1980-05-13 Shin-Etsu Polymer Co., Ltd. Pressure-sensitive multiple resistor elements
US4210895A (en) * 1977-12-15 1980-07-01 Shin-Etsu Polymer Co., Ltd. Pressure sensitive resistor elements
US4347505A (en) * 1979-01-29 1982-08-31 Antroy Enterprises, Inc. Device for controlling a circuit
US4441097A (en) * 1979-01-29 1984-04-03 Antroy Enterprises, Inc. Device for controlling a circuit
US4322983A (en) * 1979-02-02 1982-04-06 Shin-Etsu Polymer Co., Ltd. Method for generating electric signals and a push-button switch means therefor
US4279188A (en) * 1979-09-21 1981-07-21 Scott Robert D Acoustic coupling free electric drum
EP0236222A1 (fr) * 1986-02-26 1987-09-09 Commissariat A L'energie Atomique Matériau piézorésistif utilisable pour la réalisation de sondes piézorésistives et procédé de fabrication de ce matériau
US4900588A (en) * 1986-11-11 1990-02-13 Sharp Kabushiki Kaisha Method for the production of a carbon electrode
US4906192A (en) * 1986-12-18 1990-03-06 Smithard Michael A Electronic computerized simulator apparatus
US4837548A (en) * 1987-02-05 1989-06-06 Leda Logarithmic Electrical Devices For Automation S.R.L Electric resistor designed for use as an electric conducting element in an electric circuit, and relative manufacturing process
US5305644A (en) * 1989-03-14 1994-04-26 Ercon, Inc. Force sensor
US5536568A (en) * 1991-03-12 1996-07-16 Inabagomu Co., Ltd. Variable-resistance conductive elastomer
US5510783A (en) * 1992-07-13 1996-04-23 Interlink Electronics, Inc. Adaptive keypad
US5808540A (en) * 1995-11-20 1998-09-15 Wheeler; M. Rex Position sensing and signaling system
WO1997018754A1 (en) * 1995-11-20 1997-05-29 Postur Phonic Technologies, Inc. Bio feedback sensor system
US6107612A (en) * 1998-01-26 2000-08-22 Martinex R & D Inc. Heating device and method
EP1020544A3 (en) * 1999-01-15 2001-09-19 Malat Division, Israel Aircraft Industries Ltd. Reactor for electrolytic reduction of CR+6
US6416637B1 (en) * 1999-01-15 2002-07-09 Israel Aircraft Industries Ltd. Reactor for electrolytic reduction of Cr+6
US6646540B1 (en) * 1999-06-22 2003-11-11 Peratech Limited Conductive structures
US20040207506A1 (en) * 2001-02-08 2004-10-21 Bruce Bower Current control device
US6943660B2 (en) * 2001-02-08 2005-09-13 Qortek, Inc. Current control device
US7186356B2 (en) 2001-06-07 2007-03-06 Peratech Ltd. Analytical device
US20050128047A1 (en) * 2003-03-25 2005-06-16 Tomoyasu Watanabe Pressure-sensitive resistor and pressure-sensitive sensor using the same
US7068142B2 (en) * 2003-03-25 2006-06-27 Denso Corporation Pressure-sensitive resistor and pressure-sensitive sensor using the same
US9027408B2 (en) 2007-01-24 2015-05-12 Swelling Solutions, Inc. Elastomeric particle having an electrically conducting surface, a pressure sensor comprising said particles, a method for producing said sensor and a sensor system comprising said sensors
US20100130889A1 (en) * 2007-01-24 2010-05-27 Convatec Technologies Inc. Elastomeric particle having an electrically conducting surface, a pressure sensor comprising said particles, a method for producing said sensor and a sensor system comprising said sensors
US8298447B2 (en) * 2007-06-22 2012-10-30 Samsung Electro-Mechanics Co., Ltd. Conductive paste, printed circuit board, and manufacturing method thereof
US20080314619A1 (en) * 2007-06-22 2008-12-25 Samsung Electro-Mechancs Co., Ltd. Conductive paste, printed circuit board, and manufacturing method thereof
US20150340135A1 (en) * 2013-05-21 2015-11-26 Boe Technology Group Co., Ltd. Variable resistance and manufacturing method thereof
US9728309B2 (en) * 2013-05-21 2017-08-08 Boe Technology Group Co., Ltd. Variable resistance and manufacturing method thereof
US20150268087A1 (en) * 2014-03-24 2015-09-24 Deringer-Ney, Inc. Apparatuses and methods for fuel level sensing
US9435680B2 (en) * 2014-03-24 2016-09-06 Deringer-Ney, Inc. Apparatuses and methods for fuel level sensing
US9488515B2 (en) 2014-03-24 2016-11-08 Deringer-Ney, Inc. Apparatuses and methods for fuel level sensing
US9773485B2 (en) * 2014-05-19 2017-09-26 Skoogmusic Ltd Control apparatus
US20170092249A1 (en) * 2014-05-19 2017-03-30 Skoogmusic Ltd Control apparatus
US20170089782A1 (en) * 2014-06-18 2017-03-30 Stbl Medical Research Ag Strain gauge device and equipment with such strain gauge devices
EP3292812A1 (en) * 2016-09-12 2018-03-14 Heraeus Deutschland GmbH & Co. KG Piezoresistive material
WO2018046725A1 (en) * 2016-09-12 2018-03-15 Heraeus Deutschland GmbH & Co. KG Piezoresistive material
CN109661195A (zh) * 2016-09-12 2019-04-19 贺利氏德国有限两合公司 压阻材料
US20250004075A1 (en) * 2021-07-06 2025-01-02 Koninklijke Philips N.V. Electrical connection for use in cryogenic applications
WO2023027640A3 (en) * 2021-08-26 2023-04-27 Nanyang Technological University Binder-free stretchable interconnect

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GB1231729A (enrdf_load_stackoverflow) 1971-05-12
FR2021138A1 (enrdf_load_stackoverflow) 1970-07-17
DE1952678A1 (de) 1970-06-25

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