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EP-3982094-B1 - HEAT SENSOR CABLE WITH CERAMIC COIL AND EUTECTIC SALT BETWEEN INNER AND OUTER CONDUCTORS

EP3982094B1EP 3982094 B1EP3982094 B1EP 3982094B1EP-3982094-B1

Inventors

  • VARNELL, JAMES ALLEN

Dates

Publication Date
20260506
Application Date
20210930

Claims (11)

  1. A method of manufacturing a heat sensor cable (100), the heat sensor cable (100) including: a conductor (110) defining a conductor first end (120) and a conductor body (130) extending by a first longitudinal span (135) from the conductor first end to a conductor second end; a coil (150) that is non-conductive and includes a coil first end (160) and a coil body (170) extending by a second longitudinal span (175) from the coil first end to a coil second end, wherein the coil (150) surrounds the conductor (110) from the conductor first end to the conductor second end; an outer sheath (190) that is conductive and includes an outer sheath first end (200) and an outer sheath body (210) extending by a third longitudinal span (215) from the outer sheath first end to an outer sheath second end, wherein the outer sheath (190) surrounds the coil (150) from the conductor first end to the conductor second end; and an eutectic salt (230) that is disbursed between the conductor and the outer sheath; the method comprising obtaining said conductor (110); surrounding the conductor (110) with said coil (150); surrounding the coil (150) with said outer sheath (190); and the method characterised by : disbursing said eutectic salt (230) between the conductor (110) and the outer sheath (190); wherein: surrounding the coil (150) with the outer sheath (190) includes pulling the conductor that is surrounded by the coil through the outer sheath; and disbursing the eutectic salt (230) between the conductor (110) and the outer sheath (190) includes: melting the eutectic salt (230); drawing the eutectic salt, when melted, under vacuum into the heat sensor cable, within the outer sheath, to occupy a space defined between the outer sheath, the conductor, and the coil; and cooling the eutectic salt so that it solidifies.
  2. A heat sensor cable manufactured by the method of claim 1, wherein: the coil (150) is non-porous.
  3. The heat sensor cable of claim 2, wherein: the coil (150) is ceramic.
  4. The heat sensor cable of claim 2 or 3, wherein: the coil (150) is formed as a spring.
  5. The heat sensor cable of any of claims 2-4, wherein: the outer sheath (190) is a metal sheath.
  6. The heat sensor cable of any of claims 2-5, wherein: the outer sheath (190) is formed of an austenitic nickel-chromium-based superalloy.
  7. The heat sensor cable of any of claims 2-6, wherein: the conductor (110) is a wire.
  8. The heat sensor cable of any of claims 2-7, wherein: the heat sensor cable is coiled into a bulk length of greater than 3.05 meters (ten feet), so that the heat sensor cable is configured for storage.
  9. An aircraft (10) comprising: an electronic controller (50); an airframe (15); a bleed air duct (40) distributed in the airframe and in fluid communication with an aircraft engine supported by the airframe; the heat sensor cable (100) of any of claims 2-8, operationally connected to the bleed air duct and the electronic controller (50) of the aircraft, whereby a controller is configured for identifying for an overheat condition upon detecting an electrical short between the conductor and the outer sheath.
  10. The method of claim 1, comprising: coiling the heat sensor cable into a bulk length of greater than 3.05 meters (ten feet) so that the heat sensor cable is configured for storage.
  11. A method of installing a heat sensor, including: manufacturing the heat sensor cable according to any one of claims 1 or 10; and connecting the heat sensor cable to a controller configured for identifying for an overheat condition upon detecting an electrical short between the conductor (110) and the outer sheath (190).

Description

BACKGROUND Exemplary embodiments pertain to the art of cables and more specifically to a heat sensor cable formed with a ceramic coil and a eutectic salt between inner and outer conductors. Aircraft turbine engines are the source of "bleed air" used to support various systems on the air vehicle. The bleed air is taken from the high or low compressor sections of the turbine engine, depending upon the features and design of a particular engine. Bleed air temperatures can range from 400°F/200°C to over 900°F/483°C. Typical aircraft systems that utilize bleed air are anti-icing, environmental control systems, cabin pressurization, powering pneumatics actuators, etc. The bleed air is routed to these systems via ducts routed through the aircraft. Temperatures in these ducts can get extremely high, and if one of the ducts were to rupture or leak, there is a high potential of causing structural damage to the aircraft. Heat sensor cables in the form of linear overheat sensing elements are used in an Overheat Detection System (OHDS) to protect aircraft structure and equipment by detecting over-temperature conditions caused by high temperature pneumatic bleed air duct leakages or failures. A system consists of multiple "detection loops" installed in various zones of the aircraft monitored by Bleed Monitoring Computers (BMCs). Each detection loop includes one or more linear overheat sensing elements connected in series, and interfaces with aircraft wiring that is connected to the BMCs. These detection loops are installed along the bleed air ducts and sense when the local ambient temperature rises above a predetermined alarm temperature threshold, indicating that a duct leak or rupture has occurred. When an alarm condition occurs, the BMCs have the capability to shut down a portion or all of a duct, and also re-route the bleed air by way of another/alternate duct. The alarm temperature threshold is typically determined by where the overheat sensor is located in the aircraft. For example, overheat sensor elements that are located near the aircraft engines where the bleed air originates would have a high alarm temperature threshold, but as the air travels down the duct it cools, and the alarm threshold can be at a lower temperature. The overheat sensor element lengths can range in length from 30.5 cm (1 foot) to 4.88 meter (16 feet). An electrical connector resides at each end of the overheat sensor element to enable it to be connected to the aircraft wiring, or to another linear overheat sensor. Some "detection loops" can be over 30.5 meter (100 feet) in length when multiple linear overheat sensors are connected in series. The overheat sensor elements may be formed by pulling a molten eutectic salt with a vacuum between a conductive sheath and a conductor wire that are separated from each other by a porous ceramic, which may be provided in the form of ceramic beads. When the sensor element rolled or coiled prior to use, the ceramic may fracture or break. The ceramic, together with the molten eutectic salt, may accumulate to cause a "log jam" of debris, causing improper/incomplete filling, creating areas that can be void or partially void of salt. Such voids may be difficult and time consuming to detect. Having an area which is void of the eutectic salt may cause a longer detection time of a bleed air duct leak or rupture. US 2016/0161345 A1 discloses a heat sensor cable. A conductive core is first coated with an eutectic salt layer formulated to provide desirable thermal response characteristics. Then a non-conductive (ceramic/glass) fiber is wound around the core, after which a conducting sheath is disposed over the fiber. BRIEF DESCRIPTION Disclosed is a heat sensor cable as defined in claim 2. In addition to one or more of the above disclosed aspects of the cable, or as an alternate, the coil is ceramic. In addition to one or more of the above disclosed aspects of the cable, or as an alternate, the coil is formed as a spring. In addition to one or more of the above disclosed aspects of the cable, or as an alternate, the outer sheath is a metal sheath. In addition to one or more of the above disclosed aspects of the cable, or as an alternate, the outer sheath is formed of an austenitic nickel-chromium-based superalloy. In addition to one or more of the above disclosed aspects of the cable, or as an alternate, the conductor is a wire. In addition to one or more of the above disclosed aspects of the cable, or as an alternate, the heat sensor cable is coiled into a bulk length of greater than 30.5 meter (ten feet) so that the heat sensor cable is configured for storage. Further disclosed is an aircraft including: an airframe; a bleed air duct distributed in the airframe and in fluid communication with an aircraft engine supported by the airframe; the heat sensor cable disclosed hereinabove, operationally connected to a blead air duct and an electronic controller of the aircraft, whereby a controller is configured for iden