Abstract: A fuse that can be made small while improving its breaking performance. An element 3 is securely held between the two lengthwise ends of a tubular fuse casing 2 and a pair of metal plates 4 having a melting point of more than 1000° C. The ends of the fuse casing 5 are respectively pushed into caps 5 so that the caps are fitted to the fuse casing 2 in such a manner as to cover the metal plates 4. The metal plates 4 protect the caps 5 from direct exposure to an arc discharge, which occurs when the element 3 fuses due to an overcurrent. Even if the fuse casing is made small, the metal plates 4 reliably interrupt overcurrent by absorbing the energy of an arc discharge.

Abstract: A fuse that can be made small while improving its breaking performance. An element 3 is securely held between the two lengthwise ends of a tubular fuse casing 2 and a pair of metal plates 4 having a melting point of more than 1000° C. The ends of the fuse casing 5 are respectively pushed into caps 5 so that the caps are fitted to the fuse casing 2 in such a manner as to cover the metal plates 4. The metal plates 4 protect the caps 5 from direct exposure to an arc discharge, which occurs when the element 3 fuses due to an overcurrent. Even if the fuse casing is made small, the metal plates 4 reliably interrupt overcurrent by absorbing the energy of an arc discharge.

Abstract: An improved compact fuse has a fusible metal wire stretched between a pair of metal terminals. The wire and the portion of the terminals to which the wire is connected are enclosed in an envelope made of insulation material. The ends of the terminals protrude outside the envelope. The envelope is filled with silicon cellular resin to cover the wire and create many sectioned spaces that dissipate the thermal energy generated when the wire melts from overcurrent, thereby preventing damage to the envelope. When heated by vaporization of the fusible metal wire, the silicon cellular resin generates byproducts which rapidly extinguish the arc.

Abstract: A method for making a PTC element grafts a crystalline polymer to conductive particles to form a PTC composition. The step of grafting including solution polymerization. The PTC composition is formed into a PTC element. The PTC element is cross-linked after forming. The PTC element according to this invention exhibits superior PTC behavior when the temperature of the PTC element reaches the crystal melting point of the crystalline polymer.

Abstract: A PTC device has two electrodes affixed to opposed surfaces. The electrodes consist of a metal foil having a conductive layer on their surfaces that contact the PTC material. The conductive layer has a thermal coefficient of expansion intermediate between the thermal coefficients of expansion of the metal foil and the PTC material. The intermediate value of the thermal coefficient of expansion of the conductive layer prevents peeling of the electrodes off the PTC element due to the variation of the temperature of the PTC device resulting from repeated voltage applications. In addition, improved adhesion of the electrodes to the PTC material reduces resistance changes after repeated temperature cycling.

Abstract: A PTC element displaying low volume resistivity and excellent PTC characteristics contains conductive carbonaceous particles having a large particle size, small specific surface area and being essentially unstructured such particles being, for example, thermal black or mesocarbon microparticles. The conductive particles are heat treated in an inactive atmosphere, blended with a crystalline polymer and then cross-linked by gamma radiation. In a variant form, the polymer can be chemically grafted onto the particles. The very low resistivity and excellent PTC characteristics of this PTC device make it suitable for miniaturization.

Abstract: A self-recovery PTC device for overcurrent protection of electrical circuits is made with a polymer/metal powder composition electrode that displays stable resistivity over a broad range of contact forces. Secure bonding of electrodes to a PTC element is achieved because both components are polymer composites, eliminating the problems associated with attempts to bond metal electrodes to a polymer PTC element. Swelling of metal electrodes, that results from outgassing by a PTC element, is also eliminated, because polymer electrodes are gas permeable.

Abstract: A positive temperature coefficient ("PTC") device body is formed by compression molding of an organic PTC composition consisting of a crystalline polymer with conductive particles dispersed therein. The body is sandwiched between electrodes to which terminals are attached by spot welding or soldering. The PTC device body is aged at normal pressure and at a temperature higher than the peak resistance temperature, that is, the temperature at which its resistance is a maximum, and lower than 250.degree. C. The resistance of the PTC device does not change either before or after exposure to high temperatures, that is, temperatures substantially greater than 250.degree. C., and the PTC characteristics of the device do not decrease despite aging. Therefore PTC devices made according to the present invention can be surface-mounted.

Abstract: A self-resetting overcurrent protection element uses an element body made up of a mixture of polymers and carbon black grafted with polymers. A resilient sheathing material covering the element body permits free expansion of the element body to permit the resistance of the overcurrent protection element to increase substantially in response to Joule's heating from high current. The sheathing materials preferably are made of elastic epoxy resins or silicone resins that allow significant expansion of the element body at the time of overcurrent protection, thus increasing the ratio of resistance in the element between an overcurrent state and a normal operating state.

Abstract: A product having a positive temperature coefficient of resistance is formed by etching a carbon black at an elevated temperature to remove less crystalline portions and thereby to increase the specific surface area of the carbon black. The resulting carbon black is called porous carbon black. The porous carbon black is blended with a crystalline polymer to form a product having the desired positive temperature coefficient of resistance. Production of a material suitable for use as a resettable fuse is described.

Abstract: A process for producing a self-restoring overcurrent protective device by the grafting method, wherein an organic peroxide is added to colloidal graphite, at least one kind of carbon black selected from among acetylene black, Ketjen black and furnace black having a high structure, and at least one kind of crystalline polyner substance while heating and milling the latter three components, and the heated mixture having a high viscosity is forcibly milled, whereby the organic peroxide is reacted with the polymer substance to give unpaired electrons to the polymer substance to thereby form polymer radicals. Subsequently, the formed polymer radicals are preferentially grafted onto the above-mentioned graphite and carbon black to form a milled mass wherein the grafting products are homogeneously dispersed in the above-mentioned polymer substance. The milled mass is molded into a predetermined shape while it still retains thermoplasticity.