EP0364298A2 - Dispositif et procédé de détection de chaleur - Google Patents

Dispositif et procédé de détection de chaleur Download PDF

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Publication number
EP0364298A2
EP0364298A2 EP89310543A EP89310543A EP0364298A2 EP 0364298 A2 EP0364298 A2 EP 0364298A2 EP 89310543 A EP89310543 A EP 89310543A EP 89310543 A EP89310543 A EP 89310543A EP 0364298 A2 EP0364298 A2 EP 0364298A2
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EP
European Patent Office
Prior art keywords
conductor
temperature
support structure
heat
resistance
Prior art date
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Application number
EP89310543A
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German (de)
English (en)
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EP0364298A3 (fr
Inventor
Joseph Ralph Beatty
Thomas Marion Kiec
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP0364298A2 publication Critical patent/EP0364298A2/fr
Publication of EP0364298A3 publication Critical patent/EP0364298A3/fr
Withdrawn legal-status Critical Current

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    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/06—Electric actuation of the alarm, e.g. using a thermally-operated switch

Definitions

  • the present invention relates generally to a temperature sensing apparatus for the detection of temperature increases and decreases.
  • Fire loses have been, and continue to be, a major problem. This dramatic loss due to fire has prompted corporations, insurance companies and individuals to spend large sums of money annually in an effort to detect and to prevent fires and their associates loses.
  • Residential fires in the United States are estimated to be the single greatest monetary loss at approximately several billion U.S. dollars annually. One out of four households will be affected by fire in the cooking area. Total fire losses in the United States provide for approximately one percent of the gross national product. Property loss alone is estimated to cost approximately 4.5 billion dollars annually. There are approximately 2.3 million fires reported yearly.
  • the pneumatic-type detector operates on the principle that an increase in temperature causes an increase in the pressure of a confined gas. The pressure actuates a switch which in turn sends an electric signal to a control point for activating an alarm or the like.
  • Thermoelectric detectors measure a small change in electrical current which is initiated when heat is applied to the junction of two dissimilar metals.
  • the line-type thermoelectric detector consists of two pairs of wires which are enclosed in a sheath used to protect the wires from physical damage. One wire of each pair has a high coefficient of heat resistance. The wire with the same coefficient of heat resistance (one from each pair) are insulated against heat.
  • the other wires are open to temperature effects in the protected space.
  • the wires are connected to a device that measures the resistance of the wires. An increase in temperature in the protected space shows up as an unbalance in the resistance of the wires. A high enough rate of unbalancing causes the alarm to be activated.
  • Combined fixed-temperature and rate-of-rise devices can be activated when temperature rises at, or faster than, a preset rate. If the temperature rises slowly but continuously, the rate-of-rise device may not be activated. Then, the fixed temperature device will eventually initiate the alarm.
  • the primary advantage of the combined detector is the additional protection provided. The fixed-temperature device responds to a slow increase in temperature that may not activate the rate-of-rise device, which resets itself, but the fixed-temperature device does not.
  • the sensors associated with the currently used fire detection system are typically based upon antiquated technology.
  • Existing smoke detectors either can not function in many homes and industrial environments or are ineffective. The main operational difficulty results from false alarms. Industrial environments, improper placement and improper utilization result in ineffective, inoperable or false alarms. Thus, much prior work has been focused on the residential use of smoke detectors. Two main objections to the use of smoke detectors are indistinguishable "friendly smoke" from cooking and critical response awareness time. Smoke detectors have been responsible for the response and the warning of a fire in process. Noxious gases of combustion are sensed by particulate emission or by photoelectric differential. However, the detection is operational only as a function of a fire already in progress.
  • JP-A-53-144699 discloses a fire detecting sheet having layered patterns printed on conductive ink on a biaxially oriented plastic film.
  • the sheet has recesses positioned in a checkered form such that, as the film is heated to soften, it shrinks making holes and thus cutting the conductive path and causing an alarm to sound.
  • US-A-­4520352 describes a heat sensor having a continuous wire secured to a sheet or sandwiched between two or more sheets of heat migrating plastic such that, as the plastic is exposed to heat, it shrinks breaking the wire or the wire is melted causing an alarm to be activated.
  • US-A-4408904 described a plurality of meltable segments which are spaced apart one from another along the length of a conductor and in positions separating one from the other.
  • Each segment is identically fabricated from electrically conductive material having a preselected melting point below the melting points of the conductors.
  • Electrical insulators that are mounted along the conductors confine molten material that flows from the respective segments, so as to position the molten material in bridging contact between the conductors at specific locations along the length.
  • US-A-4388267 also describes a temperature profile detector which utilizes a pair of elongated electrical conductors that are spaced one from the other. When one conductor melts and bridges the space between the respective conductors, a change in resistance occurs in the conductor. The change in resistance can be related to a change in temperature. Thus, a temperature profile can be created from the change in conductance of the melted conductor.
  • Fire detectors can be classified in two categories: (1) heat activated sensors, and (2) smoke activated sensors. Both heat activated and smoke activated sensors have been extensively developed within their own technology. Nonetheless, most of the sensors which are currently used in the marketplace have been used for twenty years or more. Advances in electronics utilizing low cost semi-conductors have made the currently used electronic detector systems more affordable and has offered more sophisticated and versatile alarm mechanisms. However, the sensor technology associated with the alarm system technology has not progressed at as fast a rate as the technology associated with the electronics.
  • a temperature sensing apparatus comprising a support structure having elastic characteristics and thermal expansion characteristics sufficient for repeated expansions and contractions due to changes in temperature, and an electrical conductor operatively associated with said structure for expanding and contracting in unison with said structure whereby the expansion and contraction of said conductor causes a change in its electrical resistance whereby the temperature can be sensed by detecting its electrical resistance and a pair of leads connected to spaced locations of said electrical conductor.
  • Elasticity is generally defined as the experimental observation that the force associated with the elasticity tends to restore the original shape and size of the elastic materials.
  • the elastic force tending to restore the original size and shape to a material is proportional to the displacement of the elastic material based upon Hooke's law. Obviously, such behaviour is limited to a range of forces and displacements that do not permanently deform the elastic material.
  • Hooke's law is typically defined as the relationship between stress, the force per unit area, and strain, the fraction of elongation. The stress is proportional to the strain based upon Young's modulus of elasticity, which depends only on the material in question and not on its shape.
  • the present invention utilizes reactions of heat dissipation, coefficient of thermal conductivity, dielectric strength, specific resistance and thermoplastic polymer chemistry.
  • Thermoplastic polymers are long chain polymers that become soft when heated. They are comprised of linear branch chained polymer with little or not cross linking. when cast into thin films, end products are light in weight, have excellent chemical resistance to corrosion, and are durable. Due to their chemical structure, thermoplastic polymers also have good properties of electrical resistance, dielectric strength and specific thermal resistance. The chemical properties of thermoplastic polymers can be formulated to respond to changes in heat at very small changes in temperature or rates of change of temperature. Such responsiveness or reaction has chemical and physical influence on the film support structure.
  • Resistance opposes the flow of electrons.
  • a conductor is applied to a support structure in such a manner that the conductor adheres to the support structure and responds to physical changes in the support structure induced by temperature.
  • a potential applied across the conductor has a specific profile of measurable resistance that changes at a constant rate as temperature increases or decreases. Electronics are available to measure specific resistance points or the rate of change profiles.
  • a single conductor sensor 100 associated with the heat sensing apparatus of the present invention has as its primary components a first support structure 110, an optional support structure 130, and a conductor 120. If the second support structure 130 is provided it may be laminated to extend over the first support structure 110 and over the conductor 120.
  • the conductor 120 is fixedly and intimately secured at least to the first support structure 110. The intimate securing provides that the conductor 120 acquires the expansion and contraction characteristic of the first support structure 110.
  • the conductor 120 is illustrated "sandwiched" between the first support structure 110 and the optional support structure 130.
  • the conductor 120 has associated therewith leads 124, each affixed to the conductor 120 with a contact 122 at spaced locations.
  • the process of securing the conductor 120 to the support structure 110 can be accomplished using different techniques depending on the materials used for the support structure and the conductor as well as the use and result to be achieved.
  • the conductor 120 can be intimately secured to the support structure 110 by metallizing, laminating, pressure sensitive adhesion, thermal curing, thermal plastic lamination, ultraviolet curing, printing and electrodeposition techniques.
  • the first support structure 110 and the optional support structure 130 are each a plastic substrate, for example, make of polyethylene, polypropylene, polyester, nylon, polycarbonate, blended plastics and various fire retardant plastics.
  • the first support structure 110 and the optional support structure 130 can vary in thickness from, for example, approximately 0.5 mils to approximately 15 mils. Also, the first support structure 110 and the optional support structure 130 may differ in thickness or composition depending on the result desired.
  • the conductor 120 which is affixed between the first support structure 110 and the optional support structure 130 can comprise various conductive media.
  • the conductor 120 has been found to adequately function with vacuum metallized aluminum, printed conductive ink of silver, nickel, copper or gold, a conductive adhesive, a thin gold or aluminum foil, or most commercially available conductive coatings such as lead, nickel, copper, gold and conductive pigments.
  • the conductor 120 "take on" the physical properties associated with the first support structure 110, and possibly properties of the optional support structure 130.
  • the conductor 120 expands and contracts while maintaining its conductive properties.
  • the resistivity/con­ductivity associated with the conductor 120 changes.
  • the changes in resistivity/conductivity can be readily monitored by an electronic monitoring device, i.e., an electric circuit, which in turn can be calibrated to very accurately monitor the temperature associated with the thermal expansion of the support structures 110 and 130.
  • Fig. 2 is a circuit diagram of an alarm 814 incorporating a sensor 700 according to the invention.
  • the alarm is powered by a battery 816 and comprises a voltage comparator 804 controlling the conduction of an NPW transistor 810 which in turn controls an alarm buzzer 812.
  • the comparator 804 compares the voltages at the centre taps a, b of two voltage divides comprising, respectively, resistor 806 and the conductor of sensor 700, and variable resistor 802 and fixed resistor 808. When the voltage at a exceeds that at b, the output of the comparator 804 changes from low to high, turning on the driver transistor 810 and hence sounding the buzzer 812.
  • the threshold temperature at which the alarm trips can be set by adjusting variable resistor 802, which varies the voltage at b.
  • Fig. 3 is perspective cutaway view of the multiple conductor sensor 400 associated with the heat sensing apparatus 10 as illustrated in Fig. 6 to be described later.
  • the sensor 400 has associated therewith first, second and third conductors 410, 420, 430, laminated together with the interposition of insulating support structure layers (not shown) and connected electrically in series.
  • the first conductor 410 is connected adjacent its right end to a first lead 411 by a first contact 412, and at its left end to a second lead 413 by a contact (not shown).
  • the second conductor 420 is connected adjacent its right end to a lead 424 by a contact 422 and adjacent its left end to lead 423 by a contact (now shown).
  • third conductor 430 is connected to spaced leads 424, 442 by contacts 422, 440 respectively.
  • the multiple conductor sensor 400 can thus act as a resistance ladder with the lead 442 connected to one side of the potential to be divided and the lead 411 connected to the other side. Two intermediate potentials can thus be detected at leads 413, 423 and 424, 434 respectively, these being determined by the resistance of the conductors 430, 420, 410 respectively.
  • temperature sensing apparatus of Fig. 3 can provide a continuous measurement of increases and decreases in temperature and sense different pre-set temperatures determined by the conductors 430, 420, 410, these temperatures being of increasing value.
  • the sensor is a flexible, positional, temperature sensor that acts as a transducer for an electronic monitoring device and reflects changes in resistivity and conductivity which occur based upon the expansion or contraction of the support structure of the sensor as the temperature increases or the temperature decreases in the vicinity of the sensor.
  • Fig. 7 illustrates an example of the heat sensing apparatus of the invention which can be used to evaluate differing temperature characteristics.
  • the circuit illustrated in Fig. 6 includes three sub-circuits A, B and C consisting of resistors 212, 222, 232 and transistors 214, 224, 234, resistors 212, 222 being variable resistors.
  • a battery 240 is connected via a switch 250 and a variable resistor 260 across the leads 411, 422 of the sensor 400.
  • the bases of each of the transistors 214, 224, 234 are connected between the switch 250 and the variable resistor 260.
  • the collectors of transistors 214, 224 are connected via light emitting diodes 216, 226 to the other side of the battery and the collector of transistor 234 is connected to the three resistors 212, 222, 232.
  • Resistor 212 is connected to lead 411 of the first conductor 410 of the sensor, resistor 222 is connected to leads 413, 423 of the first and second conductors 410, 420 respectively and resistor 232 is connected to leads 424, 434 of conductors 420, 430 respectively.
  • the sensor 400 acts as a voltage ladder and when the temperature sensor reaches a first value determined by conductor 410 transistor 214 will transmit and LED 216 will illuminate.
  • transistor 224 When a second temperature sensed by conductor 420 is reached, transistor 224 will conduct and LED 226 will illuminate and finally when the temperature is reached which is sensed by conductor 430, transistor 234 will conduct and alarm 300 will sound.
  • One subcircuit of a modified control circuit could be a simple wire connector adapted for use without utilizing the change in resistance characteristics.
  • the wire connector subcircuit can be used as a monitoring device against which another subcircuit can be compared or evaluated.
  • Fig. 4 is a graph of resistance versus temperature for a heat sensor as illustrated in Fig. 3.
  • the abscissa reflects increasing temperatures and the ordinate reflects increasing resistance. It is readily observable that the resistance increases at a very proportional rate with respect to temperature.
  • the directly proportional relationship between resistance and temperature for sensors which practice the present invention is readily adapted for use in an alarm system.
  • Fig. 5 is a graph of resistance versus time and temperature for a single heat sensor as illustrated in Fig. 4.
  • the ordinate indicates increasing resistance in ohms with displacement from the origin.
  • the abscissa, with displacement form the origin, reflects increasing time as well as increasing and decreasing temperature with respect to the time throughout an experiment.
  • Particularly of interest for the heat sensing apparatus 10 of the present invention is the trimodal curve 600.
  • the trimodal curve 600 comprises the first peak 610, the second peak 620 and the third peak 630.
  • each peak 610, 620 and 630 is directly associated with a heating period as reflected by increasing time.
  • the temperature increased to 193°C at the beginning or base of each peak.
  • the increase in temperature was provided in a step temperature function.
  • the temperature was increased immediately to 193°C whereby the first peak began to rise.
  • the temperature was reduced to ambient room temperature and the first peak 610 immediately dropped.
  • the temperature was again increased in the vicinity of the heat sensing apparatus.
  • the temperature increased immediately to 193°C resulting in the increase of the second peak 620.
  • the temperature was reduced to ambient room temperature and the second peak 620 immediately dropped.
  • a step function of heat was applied with the same results.
  • the heat was applied to the heat sensing apparatus for consecutively shorter periods of time.
  • the coefficient of thermal expansion can be adjusted to effect the conductor and to cause a change in the resistance/con­ductivity.
  • the support structure expands, the conductor expands and the resistance/conductivity changes.
  • the support structure and the conductor expand equal amounts.
  • the changes in resis­tance/conductivity can be measured and correlated to a temperature increase or a temperature decrease.
  • the support structure material and the conductor material are selected based upon the specific situation in which the heat sensing apparatus is to be used.
  • Characteristics which should be considered when selecting conductor materials or support structure materials are the linear coefficient of thermal expansion of the materials, the elasticity of the materials, Young's modulus of the materials, the bulk modulus of the materials, Poisson's ratio for the materials and the compressibility of the materials. Additionally, other physical parameters and characteristics of the materials may be relevant based upon the use to which the invention is applied and the result desired.
  • the first support structure and the second support structure may differ in material to alter the overall coefficient of thermal expansion of the combination and ultimately the resistance/conductivity profile of the conductor 120.
  • an expansion bias can be created.
  • the expansion bias can be used to alter the expansion of constriction characteristics of the conductor 120.
  • Such physical changes in the support structures 110 and 130 can significantly alter the electrical properties of the sensor 100 and exhibit a change in the resistance/con­ductivity profiles as illustrated in Figs. 4 and 5.
  • thermoplastic film is used by casting the thermoplastic into a film having a thickness 0.25 to 25.0 mils.
  • a metal conductor is physically associated with the thermoplastic support structure. The metal conductor can be deposited by vacuum deposition, ion sputtering, chemical vapour plating and glow discharge as well as other similar techniques.
  • a thin single or multi-layered coating is applied to the support structure by deposition of the coating metal from its vapour phase.
  • Vacuum evaporated films, or vacuum metalized films, of aluminum, silver and gold are most common. Such vacuum deposited films are applied by vaporizing the metal in a high vacuum and then allowing the vaporized metal to condense on the film to be coated. Vacuum-metalized films are extremely thin ranging from 0.002 to 0.3 mils.
  • vapour deposited films can be produced by ions sputtering, chemical vapour plating and a glow discharge process.
  • ion sputtering a high voltage dispelled to a target of the coating material in an ionized gas media causes ions (atoms) to be dislodged and then to condense as a sputtered coating on the base or support structure.
  • chemical-vapour plating a film is deposited when a metal bearing gas thermally decomposes on contact with a heated surface of the base or support structure.
  • a gas discharge deposits and polymerizes the plastic film on the base or support material.
  • conductive inks can be used. Conductive inks contain a conductive pigment of silver, indium, tin, nickel, iron and the like which provide electrical characteristics.
  • the hotter the material the more resistance the material will have if used as a conductor.
  • the atoms making up these materials vibrate more and collide with electrons as they try to travel through the material. With such materials, the resistance increases as the temperature increases.
  • the thermoplastic support structure Due to the thickness of the support structure, heat transfer is almost immediate.
  • the thermoplastic support structure begins to react, transferring heat energy through its length in the plastic. This phenomena is called heat dissipation.
  • the metal coating itself reacts with the thermoplastic responding to the heat transfer in changing electrical resistance. Due to the nature of the metal coating, the material will remain in ultimate contact with the support film and continue to transfer electrons until a separation of the film by melting is initiated. The support film cannot respond so quickly as to interfere with the conductivity of the metal.

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  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
  • Fire-Detection Mechanisms (AREA)
EP19890310543 1988-10-13 1989-10-13 Dispositif et procédé de détection de chaleur Withdrawn EP0364298A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US25804688A 1988-10-13 1988-10-13
US258046 1988-10-13

Publications (2)

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EP0364298A2 true EP0364298A2 (fr) 1990-04-18
EP0364298A3 EP0364298A3 (fr) 1990-12-19

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EP19890310543 Withdrawn EP0364298A3 (fr) 1988-10-13 1989-10-13 Dispositif et procédé de détection de chaleur

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EP (1) EP0364298A3 (fr)
JP (1) JPH02236428A (fr)
AU (1) AU4290889A (fr)
CA (1) CA2000611A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170228994A1 (en) * 2016-02-10 2017-08-10 Kidde Technologies, Inc. Pneumatic fire detectors

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3720900A (en) * 1969-07-08 1973-03-13 Mettler Instrumente Ag Thin-film resistance thermometer having low ohmic contact strips
EP0128601A1 (fr) * 1983-05-10 1984-12-19 Leuven Research & Development Dispositif de contrôle de température
FR2571493A1 (fr) * 1984-10-05 1986-04-11 Gradient Fluxmetre thermique a resistances

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3720900A (en) * 1969-07-08 1973-03-13 Mettler Instrumente Ag Thin-film resistance thermometer having low ohmic contact strips
EP0128601A1 (fr) * 1983-05-10 1984-12-19 Leuven Research & Development Dispositif de contrôle de température
FR2571493A1 (fr) * 1984-10-05 1986-04-11 Gradient Fluxmetre thermique a resistances

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170228994A1 (en) * 2016-02-10 2017-08-10 Kidde Technologies, Inc. Pneumatic fire detectors
US10002508B2 (en) * 2016-02-10 2018-06-19 Kidde Technologies, Inc. Pneumatic fire detectors

Also Published As

Publication number Publication date
EP0364298A3 (fr) 1990-12-19
AU4290889A (en) 1990-04-26
CA2000611A1 (fr) 1990-04-13
JPH02236428A (ja) 1990-09-19

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