GB624565A - Improvements in or relating to electrical resistances and circuits and apparatus for use therewith - Google Patents

Abstract

624,565. Non-metal resistances ; temperature-variable resistances ; resistance coatings and deposits ; compression resistances ; powdered and granular resistances. ROBERTS, G. E. Jan. 3, 1946, No. 289. [Class 37] [Also in Groups XI, XXI, XXXV, XXXVII, XXXVIII, XXXIX and XL (c)] A resistor which possesses a non-linear and negative resistance/temperature relationship comprises amorphous boron, which constitutes or is a component of the resistance element, and contacting electrodes formed of a metal with which amorphous boron will not alloy ; copper or silver fulfil this requirement. The construction may be such that a resistor according to the invention is variable by compression in addition to temperature. In Figs. 1a and 1b a flat insulating former 10 wound with separated copper wires 11, 12 is inserted in a flexible envelope 13 which is then filled with amorphous boron 17. In Figs. 2 and 2a silk veil 20 is sandwiched between copper sheets 18, 19 with the cells 21 in the veil filled with amorphous boron ; this construction is pressure responsive in that the copper sheets are flexible. In Fig. 4 (not shown) perforated mica sheets are sandwiched between copper plates with amorphous boron occupying the perforations. Fig. 3 (not shown) illustrates another construction in the form of a coaxial line section wherein porcelain beads spaced around the inner conductor define areas filled with amorphous boron. A further construction, Figs. 5 and 5a, utilizes two rectangular strips of copper foil 30, 31 which are rolled together after coating adjacent sides with a paint 32, 33, formed of amorphous boron in cellulose or molten wax. Fig. 6 (not shown), depicts amorphous boron made into a paste with cellulose occupying the area within a test tube not occupied by an inner tube wound with two copper. wires. For high temperature working, for example above 100‹ C. the amorphous boron is suspended in glass or a ceramic. Amorphous boron paint may be applied as a coating on connecting terminals (or leads) to electrical apparatus such that the terminals are connected together through the paint which at ordinary temperatures is an insulator. The Specification illustrates numerous practical uses of the various forms of construction.