GB743326A - Improvements in or relating to apparatus for providing protection against fires and/or explosions - Google Patents

Abstract

743,326. Fires &c. preventing &c. WILKINSON SWORD CO., Ltd., GRAVINER MANUFACTURING CO., Ltd., RANDOLPH, H. B., and MATHISEN, A. April 10, 1953 [April 21, 1952]. No. 9919/52. Class 47 [Also in Group XXIX] An arrangement for detecting damage to the wall of a space-enclosing structure, such as an aircraft fuel tank, comprises at least one conducting member having an extensive surface area and arranged close to the wall of the structure, so that when the wall is damaged the conducting member or members is or are also damaged thereby altering the conditions in an electric circuit controlling the provision of explosion and/or fire suppressing substances. In an embodiment employing a single conducting member of extensive area, the member 41 consists of closely spaced windings of resistance wire made somewhat similarly to an electrically heated blanket. The member 41 which is arranged in contact with an aircraft fuel tank is placed in one arm of a Wheatstone bridge comprising a relay 47. Unbalancing of the bridge circuit due to damage of the tank and thus to the element 41 completes the circuit through contact 48 and causes container 21 to liberate suitable fire and/or explosion suppressing substances. In other embodiments two conducting sheet members are used, these being separated by sheets of Kraft paper. The resulting sheet is wrapped around the enclosure to be protected, the passage of a bullet, for example, through the sheet swaging the two conductors together and completing an electric circuit. The conducting sheets may be a fine gauze mesh or may consist of thin continuous metal sheets. A further arrangement is described in which thin metal-foil sheets are arranged on the inner or outer surfaces of a fuel tank, which are coated so as to be non-conducting, so that a metal bullet or other projectile during its passage through the wall of the tank connects the inner and outer sheets electrically and completes the circuit of a high-speed mechanical or electronic relay. Specifications 691.972 and 643,188 are referred to in the Provisional Specification.