Abstract: The invention relates to bimorph electromechanical transducers made from polymer material.It specifically relates to a transducer comprising a plurality of superimposed dielectric sheets for forming a bimorph structure, whose deformations are controlled in linear manner by a voltage. None of the sheets is piezoelectric. The linearity of operation is obtained because at least one of the dielectric sheets carries a permanent electric charge.The invention is applicable to the construction of microphones, telephone receivers, loudspeakers, as well as to the construction of optical components, whose precise, small displacements it is desired to control.

Abstract: A sensing probe unit includes an electrically nonconductive polymeric layer charged with a permanent electric charge to form an electret and intimately bonded to a compensating metal electrode. In the fabrication, the polymeric layer is cleaned and the metal electrode affixed to one surface by vapor deposition, lamination or baking. The polymeric layer may also be applied by coating the electrode with dielectric particles and then heating the subassembly to fuse the particles into an integral layer and to bond the fused layer to the electrode. The subassembly is thermally destressed and the polymeric layer is thereafter charged by triboelectric charging, corona discharge or electron beam charging, or by liquid contact charging processes. In the latter, a Freon-type or other similar liquid having good wetting properties and high evaporation rate is used as a contact charging liquid which creates a particularly stable electret. The sensing probe is stored to prevent loss of charge and sensitivity.

Abstract: An electret device having an improved surface charge in terms of high potential and uniformity of charge distribution. The electret device comprises a plurality of electret elements formed in stacked layers upon each other, wherein at least the electret element located at the bottom layer is provided with a conductive electrode secured to the bottom surface of a dielectric body, and wherein each electret element is provided with a volume of surface charge of a single polarity.

Abstract: An electroacoustic transducer is provided in the form of a flexible tape formed of an inner flat metal foil 10 surrounded by a metal foil 14 and separated from the latter by an electret 12. The outer metal foil 14 is in turn surrounded by a PVC outer layer 20. This construction provides a flexible electret type of microphone with the additional advantage of immunity from ambient acoustic waves and electrical and magnetic fields.

Abstract: A telephone transmitter including an electret transducer is connected to an electrical circuit mounted in the transmitter housing. A resistor which can be of varying value is also connected to the circuit, the value of the resistor being adjusted to bring the operating characteristics within predetermined values. This is done by applying a sound signal of known frequency to the transducer and measuring the output characteristics of the transducer. This enables the suitable value of resistor to be connected into the circuit. By this means variations arising from varying atmospheric conditions at assembly, and other causes, can be allowed for. The metallized strip or film of the electret is preferably mounted with a very slight Vee shaped formation to avoid tight manufacturing tolerances which occur with a straight, or flat, strip.

Abstract: A tape transducer comprising an inner conductive strip laminate sandwiched between and totally enclosed by identical outer conductive strip laminates. The inner laminate has an inner conductive strip having opposite sides to which thin dielectric layers are bonded, the layers being electrically charged to form electrets having electrical charges of the same polarity on their outer surfaces. Each outer laminate has a conductive foil with marginal side portions overlying the side edges of the inner laminate and sealed together. The portions of the outer laminates aligned with the inner laminate are capable of simultaneously moving toward and away from the inner laminate for advantageously generating sonic waves in a transmitting mode and for efficiently generating an electrical signal in a receiving mode.

Abstract: The invention relates to a method and an arrangement which are of importance in the polarization of shaped articles from polymers. The shaped articles from polymers, polarized by the method as per invention, are finding effective application in electroacoustic converters, piezoelectric switches and in proving electromagnetic radiation within a broad spectral zone.It is possible to obtain by the method as per invention and, respectively, the arrangement as per invention, above-average values for polarization as well as for the piezoelectrical and pyroelectrical coefficients. The arrangement as described, and respectively, the method as described are characterized by the use of charge-limiting polarization capacitors.

Abstract: A method of continuously making a composite tape transducer consisting of the steps of electrically charging dielectric layers on opposite sides of a conductive inner strip to form electrets, applying wider outer laminates symmetrically to opposite sides of the electret-covered inner strip and sealing together the marginal edge portions of the outer laminates to enclose the electret-covered inner strip.

Abstract: The present invention provides a process for preparing piezoelectric film using a corona discharge device wherein a multi-layer of pellicles, of which at least one or more is a piezoelectric sensitive film and at least one other of the multi-layer is a companion pellicle (i.e. a pellicle with a conductance no less than that of the piezoelectric sensitive pellicle when the conductance is measured under the poling conditions of the corona discharge and in the direction of the discharge field), is subjected to a corona discharge between a pair of electrodes of which at least one such electrode has a textured surface.

Abstract: An electroacoustic transducer for a microphone comprises an electret wherein an additional capacitance substantially greater than the capacitance normally inherent in the electret is connected in parallel with the electret. The additional capacitance may be of the order of 10 times greater than the capacitance normally inherent in the electret and may be produced inherently in the transducer or by a separate component connected to the transducer.

Abstract: The invention relates to a flexible composite sheet designed to constitute an undersheet behaving as an electromechanical transducer in order to detect the apnea of subjects lying on it. This sheet comprises, in addition to a foil sensitive to pressure in the sense of electromechanical transduction (an electret or polarized piezo-electric foil), two film electrodes and two protective foils. Spacing shims are glued to the two foils against which they are juxtaposed. When the sensitive foil is an electret, the shims are directly interposed between the sensitive foil and one of the two electrodes. When the sensitive foil is a polarized piezo-electric foil, the shims are directly interposed between one of the electrodes and the correspoding external protective foil.

Abstract: In previously proposed arrangements for charging an electret foil the electret charge implanted varies over the area of the foil. In order to promote more even charging of the foil, the method of the invention subjects the foil to a progressively increasing electric field. One form of apparatus used to carry out the method has rollers at progressively higher potentials and electric fields are applied across the foil between these rollers and a metallized layer on the rear face of the foil which is earthed by a roller.

Abstract: Apparatus for continuously producing an elongated composite tape transducer having an inner laminate with a conductive dielectric-covered strip and two outer laminates each with a conductive foil comprises two reels containing the outer laminates and one reel containing an inner laminate, a station for electrically charging the dielectric layers on opposite sides of the inner strip, a mold for applying and sealing the outer laminates to opposite sides of the inner laminate to form the composite transducer, and a mechanism for pulling the three laminates through the apparatus. The lead end of the inner strip is electrically grounded. The charging station has two electrodes connected in parallel to a source of high DC voltage and physically positioned to make electrical contact with the dielectric layers, respectively, on opposite sides of the inner strip.

Abstract: A transducer for detecting the position of a mass includes a base, a mass disposed above the base and ohmically separated therefrom, a piezoelectric transducer for inducing relative motion between the base and the mass, typically by suspending the mass on a fluid oscillating at high frequency, an electric field generator on one of the base or the mass, and a conducting antenna on the other of the base or mass for detecting the position of the electric field with respect to the base. The oscillating fluid both supports the mass and generates displacement currents by creating relative motion between the mass and the base.

Abstract: A high molecular film for polarization is disposed on an electrode plate with an intermediate high molecular film sandwiched therebetween to form a laminated member, the intermediate high molecular film having a lower melting point than the high molecular film for polarization. The laminated member is heated at a temperature in the vicinity of the melting point of the intermediate high molecular film to fusion-weld the high molecular film for polarization to the electrode plate through the intermediate high molecular film, and then the high molecular film for polarization is polarized.

Abstract: A process for preparing polymer electrets comprising the following steps:(a) providing two electrodes in a deposition zone, said electrodes being in a spaced relationship to one another, having opposing surfaces, and being connected to an external voltage source capable of impressing an intense electric field between the opposing surfaces;(b) providing a dipolar substituted p-xylylene monomer vapor in sufficient amount to coat the opposing surfaces of the electrodes;(c) activating the power source; and(d) introducing the vapor from step (b) into the deposition zone, said zone being under vacuum and at a temperature at which the vapor will condense,whereby the vapor condenses on the opposing surfaces of the electrodes, the monomer polymerizing to parylene, coating said surfaces, and forming electrets.

Abstract: A process for preparing polymer electrets comprising the following steps:(a) providing a parylene film having one side affixed to a metal layer and grounding said metal layer;(b) charging the free side of the film with a direct current corona, the charge being of sufficient magnitude to convert the film to an electret;(c) providing p-xylylene monomer vapor in sufficient amount to coat the charged film; and(d) introducing the vapor from step (c) and the electret into a deposition zone, said zone being under vacuum and at a temperature at which the vapor will condense, whereby the electret is conformally coated with parylene.

Abstract: A stable electret made of a resinous polymer of a branched alpha-olefin [e.g., poly(4-methyl-1-pentene)] having a degree of crystallinity of at least 20%.

Abstract: A vibrating electret reed voltage generator. The reed vibration is induced by fluid pressure supplied to the reed chamber and controlled through a fluid oscillating circuit.

Abstract: A process for preparation of a polymeric piezo-electric material and material prepared by said process are described, wherein said process comprises polarizing a polymeric piezo-electric material by a polarization treatment which comprisescooling a vinylidene fluoride-trifluoroethylene copolymer from a temperature higher than the phase transition temperature of said copolymer which exists between room temperature and the melting point of said copolymer, and either maintaining the temperature range at which said copolymer possesses a maximum in dielectric constant occurs, or cooling gradually through said temperature range, while applying an electric field at least within said temperature range.

Abstract: An air pollutant and/or fire combustion sensing apparatus includes a charged insulating sensing electrode layer establishing an electric field as the result of electric dipoles and/or electric monopoles in or on the sensing layer. The layer has a high surface and bulk resistivity. The layer has a minimal water absorption at environmental humidities. The electric field of the sensing layer creates electrostatic sensing reactions with the gaseous products of combustion and environmental pollution and produces an amplification of the charge detection characteristic to alter the charge of the electrode. In a capacitive sensor, the sensing layer is mounted within and in spaced relation to a ground shield member. The sensing layer is thereby exposed and produces a sensitive capacitive detector for sensing of a wide spectrum of combustion products and the like.

Abstract: The invention relates to electromechanical transducers comprising an electret 4 between two electricity conducting electrodes 1 and 2. A solid intermediate layer 7 having a different deformability from that of the electret is placed between said electret and an electrode, the material forming said layer having an electrical resistivity higher than 10.sup.15 ohms.cm (for instance a silicone elastomer) and said layer having a smooth and continuous face in intimate contact with the whole of the useful area of the charged face of the electret.

Abstract: A technique for removing surface charges from thin film electret foils involves subjecting the foil to penetrating radiation of a dosage ranging from 1-25 krad and, subsequently, annealing the foil at a temperature ranging from 80.degree.-150.degree. C.

Abstract: An electromechanical electret transducer suitable for push-pull operation includes multiple vibratory diaphragms acoustically coupled to each other to increase the output sound pressure. Since the diaphragms physically shield the stationary electrets, the adverse environmental effects on the charge stabilities of the electrets are minimized.

Abstract: A displacement current sensor for generating electrical signals representative of relative motion between a conductor and an electric field source.The sensor includes means for generating an electric field and electrically conductive means positioned for interaction with the electric field, the field generating means and the electrically conductive means being relatively movable so that variations in the field encountered by the electrically conductive means induces a displacement current, as opposed to a conduction current, in the electrically conductive means.The field generating means preferably is fabricated from an electret formed in any one of a wide variety of geometrical shapes, such as planar, cylindrical or special geometrical configurations; the electrically conductive means may comprise one or more plates, wires, rods, or other special shapes.

Abstract: A control device comprising three mechanical elements, one of which is moe relatively to the two others and one of these elements being an electret, whereas the two others are control electrodes. The mechanical mobile element forms a portion partially cut out of a plate 3. Applications to electrical (particularly telephone exchanges and optical information display) switching.

Abstract: The invention relates to electret bistable systems comprising two fixed electrodes forming a capacitor. A sheet of electret material is inserted for creating holding forces in two rest positions of a moving element located in the capacitor gap. In accordance with the invention, the electret sheet is separated from the corresponding fixed electrode by a layer of dielectric which can be an air gap. As a variant, the charge density of the electret sheet may be concentrated in islands for reducing the holding forces.

Abstract: Organic piezoelectric elements having a piezoelectric modulus of the order of as high as 10.sup.-6 c.g.s.e.s.u. or more are obtained from a film, sheet or other shaped structure of a high molecular weight copolymer of 99 to 50% by weight of vinylidene fluoride with, correspondingly, 1 to 50% by weight of a comonomer, by heating the shaped structure to a temperature of 40.degree. to 200.degree. C. in an electrostatic field of an electropotential gradient of 30 to 1,500 KV/cm.

Abstract: The present invention is an improvement in electretized filtering means. This is an electric charge holding structure wherein the filter medium is covered on two opposite sides with an electrically conductive material having an air permeability that does not impair the air permeability of the filter and these two opposite sides are shorted together. This concept is similar to causing a short in the magnetic lines of force for the purpose of long time retention of the magnetic force as often employed in the vicinity of a permanent magnet. In this invention this idea is applied to electret as an air-filter medium.

Abstract: The utility of a coaxial electret cable transducer as a hydrophone at shallow depths (low hydrostatic pressure) is extended for operation at substantially greater depths (high hydrostatic pressure) by the combination of the electret with a polymer material having piezoelectric properties, i.e., a piezoid. The electret and piezoid are separate flexible materials radially stacked within the cable or alternatively and preferably constitute a single material formed to have both electret and piezoelectric properties. One substance useful as the piezoid or as the electret-piezoid combination is polyvinylidene fluoride (PVF.sub.2).The invention also comprehends the method of measuring underwater soundings at either low or high hydrostatic pressures with the aforementioned coaxial cable as an electrostatic transducer by measuring electrical signals generated across the cable conductors when the ambient pressure is low and as a piezoelectric transducer across the conductors when such pressure is high.

Abstract: The permanent electric polarization is imparted to the sensitive element by electronic bombardment within an enclosure wherein prevails a rarefied atmosphere and in which said bombardment is followed with a coating of the so-polarized sensitive element with a film of liquid of very low saturated vapor pressure whose dielectric strength is higher than that of the rarefied air of the enclosure and having advantageously lubricating properties.

Abstract: A method for rendering glass nonfogging (to condensation fog) by sandwiching the glass between two electrodes such that the glass functions as the dielectric of a capacitor, a large alternating current (AC) voltage is applied across the electrodes for a selected time period causing the glass to absorb a charge, and the electrodes are removed. The glass absorbs a charge from the electrodes rendering it nonfogging. The glass surface is undamaged by application of the AC voltage, and normal optical properties are unaffected. This method can be applied to optical surfaces such as lenses, auto windshields, mirrors, etc., wherever condensation fog on glass is a problem.

Abstract: The invention relates to bistable systems using electrets. The invention provides a three-electrode system in which the movement of the moving armature is obtained by means of biasing voltages applied to the fixed electrodes. A switching voltage applied between the moving electrode and one of the fixed electrodes releases the electrostatic holding forces generated by the electrets.

Abstract: A position indicator is arranged for detecting and indicating the position of a member that is movable along a predetermined path in discrete steps as part of the diaphragm of a still camera. Elements that can produce an electrostatic field and can scan an electrostatic field are alternatively arranged so that a single one of the elements moves with the diaphragm member along a path past a plurality of the other elements positioned along the path. The scanning elements are arranged to operate a switch that can be switched with practically no consumption of power in response to the position of the member, and the switch is arranged to energize at least one indicating element. The electrostatic-field is preferably produced by an electret, the scanning element is preferably an electrode, and the switch is preferably an MOS field-effect transistor.