Abstract: An electrical device in which a conductive terminal is physically and electrically attached to a laminar resistive element by means of a laminar conductive element. The three layers are positioned in such a way that the periphery of the conductive element does not extend beyond the first periphery and at least a part of the periphery of the conductive terminal lies within the first periphery. In a preferred embodiment the conductive element is solder and the periphery of the conductive terminal is shaped in such a way that no excess solder bridges from one laminar surface of the resistive element to the other. Devices of the invention are useful as circuit protection devices.

Abstract: The invention relates to joining insulated elongate conduit members, such as thermally insulated pipes. A pipe (1) is provided with thermal insulation (2), in which, at an end of the pipe, there is an annular recess (6) such that an end portion (4) of the pipe is exposed to allow access for connection thereto. To make a connection, a recoverable connecting collar is positioned at least partially within the recess, and allowed to recover into gripping engagement with the exposed portion of the pipe. The invention obviates the necessity of reinsulating the joint region of an insulated pipe.

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" 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. Alternatively, the second component is a thick film resistor which is connected in series with the PTC element.

Abstract: A curable adhesive composition comprises a thermoplastic fluoropolymer, an elastomeric fluoropolymer, an ethylene copolymer and a crosslinking component. The composition preferably also comprises a tackifier. The crosslinking component preferably comprises a free radical generator such as a peroxide and a co-crosslinking agent comprising a multifunctional monomer. The adhesive is particularly useful with heat recoverable articles and bonds exceptionally well to fluoropolymer substrates.

Abstract: An elastomeric grommet suitable for sealing a substrate when compressed in an axial direction. The grommet is made so that an axial passageway has an inner central section of substantially constant cross-section and first and second inner end sections which taper inwardly from first and second radial surfaces, respectively, to define first and second entry portions for passage of the substrate. First and second outer end sections lie on either side of an outer central section. The outer central section defines a groove which runs circumferentially around the entire periphery of the grommet. The grommet is particularly useful for sealing a variety of sizes of strip heaters.

Abstract: Heat recoverable soldering devices comprising a heat recoverable tubular article having at least one open end, and containing a solder insert, is provided with a curable adhesive insert between the solder insert and the open end. The curable adhesive melts, flows and cures when heat is applied to recover the article. The adhesive cures such that its viscosity increases to a value of at least 1.5 its initial viscosity during recovery of the article. Curing of the adhesive inhibits flow of the adhesive through the open end of the article and/or into the solder connection formed between two (or more) elongate bodies inserted into the article.

Abstract: Conductive polymer compositions comprise carbon black or graphite dispersed in a polymer and further comprise an arc-controlling additive such as alumina hydrate. Such compositions have improved performance when subjected to electrical stress and are, therefore, particularly useful in circuit protection devices.

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 blank 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 based on polyvinylidene fluoride have improved properties when the polyvinylidene fluoride has a very regular structure which can be characterized by a low head-to-head content in the repeating units. The improved properties include electrical stability when contacted by organic fluids and/or when maintained at elevated temperatures in air. Such compositions which exhibit PTC behavior are particularly useful in the form of self-limiting heaters which are immersed in organic fluids, especially flexible strip heaters for heating diesel fuel before it passes through a fuel filter.

Abstract: An electrical connector for an electrical lead which has a first conductor and a second conductor. The connector has a first component, a conductor-receiving member, into which the conductors are inserted, and second component, a conductor-connecting member. The conductor-receiving member and the conductor-connecting member are movable relative to one another between a unique mated configuration and a plurality of demated configurations. The conductor-receiving member is preferably transparent in order to visually determine the correct positioning of the conductors.

Abstract: A heat recoverable article comprising a conductive polymeric material with particular electrical properties. Preferably, when expanded from X% to Y% to render it recoverable the resistivity of the composition decreases on expansion in at least part of the X-Y expansion range. Preferably the composition exhibits a pseudo PTC ratio (peak resistivity/resistivity at 25.degree. C.) in the range 11/2-10. Preferably the composition has a resistivity which increases on recovery as measured in the direction of current flow, throughout the temperature range 20.degree. C. to T.sub.e (extrapolated end temperature). The article is preferably tubular, and the electrtical behaviour allows it to be conveniently electroded with elongate electrodes, while avoiding overheating during recovery.

Abstract: An electrical plug for connecting the first and second conductors of an electrical lead to an electrical power outlet. The plug is designed to contain a fuse. When the plug is connected to the power outlet and the fuse makes a proper electrical connection, a signal member provides a signal.

Abstract: A device assembly in which a plurality of PTC circuit protection devices are connected in series. Assemblies of this type are useful in providing protection under voltage conditions which would be unsafe for an individual protection device. In a preferred system the device assembly is connected in series with a circuit breaker.

Abstract: Conductive polymer PTC compositions have improved properties, especially at voltages of 200 volts or more, if they are very highly cross-linked by means of irradiation, for example to a dosage of at least 50 Mrads, preferably at least 80 Mrads, e.g. 120 to 600 Mrads. The cross-linked compositions are particularly useful in circuit protection device and layered heaters.

Abstract: Conductive polymer PTC compositions have improved properties, especially at voltage of 200 volts or more, if they are very highly cross-linked by means of irradiation, for example to a dosage of at least 50 Mrads, preferably at least 80 Mrads, e.g. 120 to 600 Mrads. The cross-linked compositions are particularly useful in circuit protection devices and layered heaters.

Abstract: A sealing strip, particularly for making a telecommunications splice case comprises a sintered ultra high molecular weight polyethylene strip that can weld together parts of, for example, a wrap-around sleeve.

Abstract: A sensing assembly suitable for detecting both a first event which involves the presence of an electrolyte and a second event which does not involve the presence of an electrolyte, and for distinguishing between them. The assembly comprises a first conductor and a second conductor which is electrically insulated from the first conductor in the absence of both first and second events but becomes electrically connected to the first conductor by either an ionic connection in the presence of a first event or an electronic connection in the presence of a second event. The assembly also comprises a sensing apparatus of determining whether the connection is ionic or electronic. The assembly is useful for detecting leaks of hydrocarbons, e.g. gasoline, and water in storage tanks.

Abstract: A process for preparing an electrical device which has a conductive polymer exhibiting PTC behavior. The cross-linking may be to a level of 50 to 100 Mrad or higher for devices designed to withstand high voltage test conditions. The device may be a laminar device having a center layer of higher resistivity than two surrounding layers.

Abstract: A method of joining a substrate, particularly a polymeric pipe for transporting fluids, e.g. natural gas and water, to an article which is not heat-recoverable and which comprises a conductive polymer composition. The article is heated by passing electrical current through the conductive polymer. The heated article makes direct contact with and fuses to the substrate, and is preferably a coupler which is used to join two pipes together. The conductive polymer preferably comprises carbon black dispersed in a sintered polymer, particularly ultra high molecular weight polyethylene, or carbon black dispersed in a very high molecular weight polymer, particularly polyethylene having a molecular weight greater than 150,000.

Abstract: An apparatus for displaying information comprising a resistive element, preferably a conductive polymer resistive element, adjacent to a thermochromic layer. When electrically powered, the resistive element heats the thermochromic layer above a transistion point causing the thermochromic layer to change from opaque to transparent. The resistive element exhibits PTC behavior and, therefore, does not overheat. The apparatus may be large in size and on a flexible substrate.