Abstract: Circuit protection devices which comprise a PTC conductive polymer element and a second electrical component which is thermally coupled to the PTC element and which, when a fault causes the current in the circuit to become excessive, generates heat which is transferred to the PTC element, thus reducing the time taken to "trip" the PTC element. The second component is for example a voltage-dependent resistor which is connected in series with the PTC element under the fault conditions and is thus protected from damage.

Abstract: A number of improvements to electrical devices, particularly sheet heaters, comprising conductive polymer compositions, are provided. The preferred heater has the following features (a) it comprises a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it comprises a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it comprises a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it comprises a dielectric layer intimately bonded to the resistive element and to the electrodes.The invention also provides an electrical device comprising first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.

Abstract: Novel conductive polymer compositions which exhibit useful PTC behavior are produced by cross-linking processes. By correlating the polymer, the conductive filler dispersed therein, and the cross-linking conditions, PTC compositions having desired resistance/temperature characteristics can be prepared. In particular the cross-linking can be carried out so as to provide compositions having a switching temperature around the cross-linking temperature. The invention is applicable to both elastomeric and thermoplastic polymers, and provides for the first time a method of making PTC compositions exhibiting useful PTC behavior from elastomers.

Abstract: A method of joining, repairing or reinforcing substrates, particularly polymeric pipes for transporting fluids, e.g. natural gas and water. The method makes use of an article, preferably a heat-recoverable article, which comprises a conductive polymer composition and which is heated to its recovery temperature by passing electrical current through the conductive polymer. Preferably the article is a heat-shrinkable coupler. The coupler may make direct contact with and fuse to the pipes, or there may be an insert between the coupler and the pipes. The article preferably comprises carbon black dispersed in either a sintered polymer, particularly ultra high molecular weight polyethylene or a very high molecular weight polymer, particularly polyethylene having a molecular weight greater than 150,000.

Abstract: Conductive polymer compositions, particularly PTC compositions, which contain alumina trihydrate, or another arc-controlling agent, and a lubricant or coupling agent. Advantages which can result from use of the lubricant or coupling agent include improved PTC behavior and improved adhesion to metal conductors, in particular metal foils and solid metal wires.

Abstract: In order to increase the stability of a device comprising at least one electrode and a conductive polymer composition in contact therewith, the contact resistance between the electrode and the composition should be reduced. This can be achieved by contacting the molten polymer composition with the electrode while the electrode is at a temperature above the melting point of the composition. Preferably, the polymer composition is melt-extruded over the electrode or electrodes, as for example when extruding the composition over a pair of pre-heated stranded wires.

Abstract: A number of improvements to electrical devices, particularly sheet heaters, comprising conductive polymer compositions, are provided. The preferred heater has the following features (a) it comprises a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it comprises a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it comprises a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it comprises a dielectric layer intimately bonded to the resistive element and to the electrodes.The invention also provides an electrical device comprising first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.

Abstract: A sealing device comprising a cap having a closed end and an open end and a retention member engaged with the cap at the open end of the cap. The retention member comprises a plurality of resilient projections which may be defined in the following manner. The projections are inclined away from the body of the retention member and toward the closed end of the cap at an angle alpha (.alpha.) with respect to the body wherein alpha is between about 90.degree. and 135.degree.. The projections have free inner ends defining a restricted opening. And the projections have, at their free inner ends, a chamfered surface facing away from the closed end of the cap which makes an angle theta (.theta.) with respect to the longitudinal axis of the body wherein theta is between about 30.degree. and 50.degree..

Abstract: A system, utilizing an analog pulsed signal, is for monitoring the condition of a system, by way of illustration, a multi-circuit electrically heat-traced substrate. The system senses the temperature of the substrate at the end of a heat traced circuit, converts the temperature to a pulsed signal, and drives the pulsed signal along the heat tracing to the control and distribution panel for the heat tracing in direct opposition to the AC which powers the heat tracing. A receiver converts the pulsed signal to a digital temperature read-out. Utilization of an analog pulsed signal enables the system to be used in a multi-circuit system without interference or signal mixing from adjacent circuits.

Abstract: The resistivity/temperature characteristics of PTC conductive polymers which have little or no cross-linking can be modified by stretching. The rate at which resistivity rises with temperature is increased, and the peak resistivity is decreased; however, the decrease in peak resistivity is substantially smaller than that observed with PTC conductive polymers having a high degree of cross-linking. Therefore, heat-recoverable electrical devices, particularly for covering telephone and other cable splices, comprise (a) a layer of a PTC conductive polymer which has little or no cross-linking, (2) an adjacent heat-recoverable layer of a PTC or ZTC conductive polymer which has a relatively high level of cross-linking, and (3) electrodes which can be connected to a power supply so that current passes through the layers and causes recovery of the device; preferably an uncrosslinked PTC layer is sandwiched between two cross-linked ZTC layers. Non-recoverable devices, e.g.

Abstract: A braider carrier for wide ribbon and/or composite strand is disclosed. The braider carrier guide pulley assembly includes a support, a pulley frame operatively, pivotly mounted to the support, a generally cylindrical guide pulley operatively, rotatably mounted to the pulley frame to accommodate movement of the carrier during the braiding operation, openings through the support and pulley frame at the point of pivot and aligned with the guide pulley, a delivery eye operatively connected to the pulley frame, the eye and the openings capable of holding strand to be braided against the cylindrical surface of the pulley preventing the strand to be braided from twisting during the braiding operation which pivots the pulley frame. The braider carrier bobbin assembly utilizes a magnetic clutch and a torsion spring, the spring capable of providing slack control of strand to be braided and the clutch capable of providing tensioned feed of strand as strand is wound off of the bobbin.

Abstract: A wall, floor or ceiling heater comprises a plurality of self regulating, preferably PTC conductive polymer, heater elements each of which is connected to two or more connection elements. The elements are held by a support. In a preferred embodiment the heater elements are positioned parallel to each other, and perpendicular to the connection elements. The support is preferably made from a rigid material which is hinged to allow the heater to be folded or rolled for easy transport.

Abstract: Methods, apparatus and articles for systems comprising optical fibers, in particular for feeding an optical signal into an optical fiber through the buffer thereof and for withdrawing an optical signal from an optical fiber through the buffer thereof. Preferably this is achieved with the aid of an optical coupling means which contacts and conforms to the surface of the buffer at a bent portion of the fiber. The coupling means can for example be a resiliently deformable material such as a polysiloxane. In a preferred aspect, the invention provides an apparatus and method for axially aligning , and preferably joining, the ends of optical fibers. The apparatus comprises means for holding two fibers so that the fiber ends are approximately abutting and axially aligned, adjacent means for passing an optical signal into one of the fibers through the buffer thereof, and adjacent means for withdrawing that signal from the other fiber through the buffer thereof.

Abstract: Electrical devices containing PTC conductive polymers which have been cross-linked in two steps, preferably by radiation. The conductive polymer is heat-treated above the temperature at which it begins to melt between the two cross-linking steps, and/or the cross-linking steps are such that a center section of the conductive polymer, intermediate the electrodes, is substantially more cross-linked than the conductive polymer adjacent the electrodes. The process is particularly useful for the preparation of circuit protection devices which are subject to high voltage faults.

Abstract: A method of printing an electrically conductive thick film ink onto a polymeric substrate. The ink comprises a polymeric binder, which is preferably a fluoropolymer, a solvent for the binder, and an electrically conductive filler. At the printing temperature the solvent is a latent solvent for the binder. After printing the temperature is raised, so that first the binder dissolves in the solvent, and then the solvent vaporizes and the binder cures. The ink may be applied to a conductive polymer, preferably fluoropolymer, substrate and used as a heater.

Abstract: Curable compositions which are useful for encapsulating electrical connections and for joining metals to metals, and which comprise a mixture of high and low molecular weight fluorocarbon elastomers. Preferred compositions comprise a mixture of three fluorocarbon elastomers, the first having a Mooney viscosity at 121.degree. C. of at least 120, the second a Mooney viscosity at 121.degree. C. of 80 to 110, and the third a Brookfield viscosity at 100.degree. C. of 1,000 to 4,000 centipoises, in amounts 5 to 50%, 25 to 70% and 5 to 50% respectively, based on the weight of the polymeric component. The compositions can be easily molded under heat and pressure, and after they have been cured, they have remarkable resistance to degradation by hot liquids, even under pressure. Consequently, the compositions are very useful in the manufacture of self-regulating heaters for use in heating the production tubes of oil wells.

Abstract: A number of improvements to electrical devices, particularly sheet heaters, comprising conductive polymer compositions, are provided. The preferred heater has the following features (a) it comprises a laminar resistive element and a plurality of electrodes which are so positioned that the predominant direction of current flow is parallel to the faces of the laminar element, (b) it comprises a laminar insulating element adjacent to but not secured to the electrodes and the resistive element; (c) it comprises a metallic foil, which acts as a ground plane and is positioned adjacent the insulating element but is not secured thereto; (d) it comprises a dielectric layer intimately bonded to the resistive element and to the electrodes.The invention also provides an electrical device comprising first and second members having different resistivities, and a thin contact layer of intermediate resistivity positioned between the first and second members.

Abstract: An electrical heater which comprises a fabric prepared from at least one of the electrodes and another elongate element of substantially higher resistance. The heater preferably comprises a PTC element, e.g. of a conductive polymer, to render the heater self-regulating. The PTC element may be in the form of a fiber forming part of the fabric, or a layer surrounding one of the electrodes, or a laminar element in which the fabric is embedded. The fabric can if desired be laminated to a sheet of a polymer, e.g. an insulating polymer or a ZTC conductive polymer. A shrinkable fabric heater can be made by incorporating a heat-shrinkable non-conductive filament into the fabric, perpendicular to both electrodes, and is useful for example for enclosing splices in telephone cables.

Abstract: Method for monitoring the electrical integrity of a heater and a novel heater for use in such a method. The heater includes an elongate heating member; an insulating jacket which encloses the heating member; a first electrically conductive member which surrounds the insulating jacket; a separating and insulating member which surrounds the first conductive member; and a second electrically conductive member which surrounds the first conductive member and is separated and insulated therefrom by the separating member. The method includes the step of testing the electrical relationship between the first and second electrically conductive members.

Abstract: In a laminate comprising adjacent layers composed of incompatible polymers, the adhesion between the layers is enhanced by irradiation of the laminate, and can be further enhanced by high temperature annealing of the irradiated laminate.