CA2240119A1 - Over-temperature sensor cable and electrical cord with over-temperature protection - Google Patents
Over-temperature sensor cable and electrical cord with over-temperature protection Download PDFInfo
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- CA2240119A1 CA2240119A1 CA 2240119 CA2240119A CA2240119A1 CA 2240119 A1 CA2240119 A1 CA 2240119A1 CA 2240119 CA2240119 CA 2240119 CA 2240119 A CA2240119 A CA 2240119A CA 2240119 A1 CA2240119 A1 CA 2240119A1
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Abstract
An electrical cord including over-temperature protection including a sensor adjacent an electrical conductor that detects over-temperatures and generates a sensor control signal. An interrupter electrically responsive to the sensor control signal defines the state of conductivity of the electrical conductor in accordance with the sensor control signal. Accordingly, the electrical cord may be made nonconductive when over-temperatures are sensed by the sensor. The sensor is a temperature sensitive material that has a positive temperature coefficient which exhibits changes in resistance in response to a change in temperature. Further described is a cable providing over-temperatureprotection which comprises temperature sensitive material disposed adjacent a conductor and a sense wire in the cable. An interrupt circuit interrupts electrical power to a load in accordance with temperature changes detected between the conductor and sense wire.
Further, a cable for providing over-temperature protection for a load is described wherein over-temperature sensors are located within a load and power is interrupted to the load when a sensor of the cable detects over-temperatures. The cable may power the load.
The electrical cord may be an extension cord or an appliance cord. The sensor may be a continuous fiber nearly the length of the cord or cable. Alternatively, multiple sensors connected in series may be employed.
Further, a cable for providing over-temperature protection for a load is described wherein over-temperature sensors are located within a load and power is interrupted to the load when a sensor of the cable detects over-temperatures. The cable may power the load.
The electrical cord may be an extension cord or an appliance cord. The sensor may be a continuous fiber nearly the length of the cord or cable. Alternatively, multiple sensors connected in series may be employed.
Description
Docket No.: 0267-001-1 1 1 1 OVER-TEMPERATURE SENSOR CABLE AND ELECTRICAL
CORD WITH OVER-TEMPERATURE PROTECTION
FIELD OF THE INVENTION
The present invention relates to electrical cords, and more particularly to electrical cords or cables which include safety protection.
BACKGROUND OF THE INVENTION
Electrical cords including electrical power cords, e.g., extension cords, are found in some form everywhere electrical power is utilized. While safe as a general rule, the conductor or current carrying element which comprises the power cord may generate substantial heat under certain circumstances, leading to a dangerous condition. For example, if a current flowing through a power cord causes a heat rise which exceeds a certain temperature, a change in the characteristics of the insulation surrounding the conductor can occur. This change could lead to brittleness, fl~king and breaking of the insulation which could result in exposure of conductor portions. Arcing from theexposed conductors could lead to fire or injury to people coming into contact with the heat-damaged power cord.
Current flowing through a power cord may cause a temperature rise to an extent where insulation melting and/or actual ~lre occurs. This is especially so where cords are coiled or several cords are gathered in a limited space. Numerous fires are attributed to malfunctioning and/or overheated extension cords. A method and/or apparatus which prevents excessive overheating in electrical extension cords, electrical power cords, power strips or cord sets, etc., would be well received for both in-home use and industry.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electrical extension and/or power cord which overcomes the above-described shortcomings of the prior art.
It is another object of the present invention to provide an electrical extensionand/or power cord which will render itself non-conductive upon the detection of an over-temperature condition.
It is another object of the present invention to provide an electrical power and/or extension cord which includes a temperature detector and a circuit illlell u~l device which controls the conductivity of the cord in accordance with a signal provided by the temperature detector.
It is a further object of the present invention to provide an electrical power and/or extension cord which provides over-temperature and ground fault protection.
It is yet a further object of the present invention to provide an electrical power and/or extension cord which includes a temperature detector, a ground fault detector, and a circuit illt~ll u~t device which controls the conductivity of the cord to render the cord non-conductive when an over-temperature condition, a ground fault condition or an over voltage condition is detected.
It is still a further object of the present invention to provide over-temperature protection for an electrical power and/or extension cord which is inexpensive and easily m~mlf~ctured.
It is an additional object of the present invention to provide a cable for sensing over-temperature areas of a load.
It is a further additional object of the present invention to provide an inlellul)l circuit that renders a cord non-conductive when over-temperature of a load is detected.
lt is an object of the present invention to provide a method of protecting an electrical cord from over-te~ e,~ e conditions.
It is a further object of the present invention to provide a cable with over-temperature protection employing a temperature sensitive material that responds to changes in temperature by changes in its resistance.
It is still a further object of the present invention to provide a method of sensing over-temperatures in a load.
To that end, an electrical cord such as an electrical power and/or extension cord which includes over-temperature protection is provided hereby. These and other objects of the invention are accomplished by providing an electrical cord inclll-ling over-temperature protection, comprising an electrical conductor surrounded by an insulating material; over-temperature sensor means disposed plo~imate the electrical conductor for detecting over-temperatures and generating a sensor control signal in accordance thereto;
and illte~lul)t means electrically responsive to the sensor control signal disposed within the conductive path formed by the electrical conductor for defining a state of conductivity of the electrical conductor in accordance with the sensor control signal. Additionally, there is provided a method of protecting an electrical cord from over-temperature conditions, comprising: placing an over-temperature sensor proximate an electrical conductor ~ulloullded by an insulating material; detecting over-temperatures with the sensor; generating a sensor control signal by the sensor; and il~te~ g conductivity of the electrical conductor in response to the sensor control signal when an over-temperature is detected.
In one embodiment of the invention there is provided a cable providing over-temperature protection comprising: a conductor; a sense wire; temperature sensitive material disposed adjacent the conductor and sense wire; the temperature sensitive material responding to temperature changes by change in resistance; measuring means for measuring changes in resistance to detect a change in temperature and for generating a temperature control signal when the change in temperature exceeds a predele~ ed value; and intellul~l means responsive to the temperature control signal for inlell.lpling electrical power to a load in accordance with the temperature control signal.
Further, a method of providing over-temperature protection is disclosed herein.
Another embodiment of the invention provides a cable for providing over-temperature protection for a load, comprising: over-temperature sensing means for detecting over-temperatures in a load and for generating a sensor control signal in accordance thereto; and a sense wire carrying the sensor control signal connecting the sensing means to inlellupl means; the il~lellu~ g means electrically responsive to the sensor control signal for il~lell u~ g electrical power to the load in accordance with the temperature control signal; wherein the over-temperature sensing means comprises a temperature sensitive m~teri~l that undergoes a change in resistance in response to a change in temperature.
The invention further provides a method of providing over-temperature protectionfor a load, comprising: placing over-temperature sensing means in a load; detecting over-temperatures in the load with the over-temperature sensing means; generating a sensor control signal by the over-temperature sensing means; and inlell u~ g electrical power to the load in accordance with the sensor control signal; wherein the over-temperature sensing means comprises a temperature sensitive material that undergoes a change in resistance in response to a change in temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example and not limitation in the figures of the accolllp~ying drawings in which like references denote like and corresponding parts and in which:
Fig. lA is a schem~hc diagram of an electrical power cord with over-temperature protection in accordance with the present invention;
Fig. lB is a schematic diagram of a section of cable of the embodiment of the present invention illustrated in Fig. lA;
Fig. 2A is a physical schematic diagram illustrating the cir.;u,lly of the control circuitofFig. lA;
Fig. 2B is an electrical schematic diagram illustrating the cir.;u-lly of the control circuitofFig. lA;
Fig. 3 is a schematic diagram showing the ci~iL-y of a second embodiment of the present invention with ground fault protection;
Fig. 4 is a physical sçhem~hc diagram showing the c~.iuiLIy of the control circuit for a third embodiment of the present invention;
Fig. SA is an electrical diagram showing the resistance values of the sensor fibers of the embodiment of the present invention shown in Fig. 4 before an over temperature condition;
Fig. 5B is an electrical diagram showing the resistance values of the sensor fibers of the embodiment of the present invention shown in Fig. 4 after an over temperature condition;
Fig. 6A is a schematic diagram of a fourth embodiment of the present invention for an extension cord;
Fig. 6B is a schematic diagram of a flfth embodiment of the present invention for sensing over-temperatures in a load with multiple sensors as in Fig. 4;
Fig. 6C is a schematic diagram of a sixth embodiment of the present invention for sensing over-temperatures in a load with a long continuous sensor as in Fig. 2A;Fig. 6D is a schematic diagram of a seventh embodiment of the present invention for sensing over-temperatures in a load with multiple sensors where the power cord provides power to the load;
Fig. 6E is a schematic diagram of an eighth embodiment of the present invention for sensing over-temperatures in a load with a long continuous sensor where the power cord provides power to the load;
Fig. 6F is a schem~tic diagram of a ninth embodiment of the present invention for a power cord of an appliance;
Figs. 7A - 7D are cross-sectional views of embodiments of electrical cords with temperature detecting sensors in accordance with the present invention; and Figs. 8 - 12 are plots of resistance over temperature for form~ tions of temperature sensitive materials for lltili7.~tion in the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Operation of a first embodiment of the power cable with over-temperature protection of the present invention will now be described with lererellce to the drawings in which like references denote like and corresponding parts. In Fig. lA cord 10 is shown comprising a phase conductor, and a neutral conductor, 12 and 14, respectively, for connection to a source of power via t~rmin~ 16 and 18 and to tçrmin~l~ of a plug or load 20 and 22, respectively. The conductors and tçrmin~l~ may be implemented in any manner known to those skilled in the art for creating a conductive path through a power cable.
Cord 10 also includes a control circuit 30 for controlling conduction of currentthrough a relay coil 28. Relay coil 28 is illustrated as having inductance L. Relay coil 28 controls the state of contact switches 24 and 26, which in turn controls the conductive state of the power cord. An over-temperature sensor 32 detects a change in temperature at its location in the power cord and generates a sensor signal on line 35 in accordance with the temperature. The control circuit 30 is responsive to the sensor signal. The over-temperature sensor 32 may be a continuous fiber extending nearly the length of the cord 10.
Fig. lB shows an enlarged view of temperature sensor 32 and its interconnection with conductors 12 and 14 of cord 10. The over-temperature sensor is prefel~bly comprised of a m~teri~l which displays a positive temperature coefficient. That is, the resistance of the sensor material increases with increasing temperature. One side of sensor 32 is electrically connected to the neutral conductor 14 via wire 31. The other side of sensor 32 is cormected to the wire 35. A sensor signal on wire 35 (the sense wire) is input to the control circuit 30. Because the voltage across the sensor material is constant, a change in temperature with its concon~ilanl change in resistance will define a current (or voltage) change through the sensor. The sensor signal is generated thereby.
Fig. 2A is a physical schem~tic diagram showing in detail one embodiment of a control circuit 30 and its connection to conductors 12 and 14 and the over-temperature sensor 32 which may be utilized for the present invention. Control circuit 30 is located within housing 34 which also holds a fixed resistance RX and relay coil 28 as well as switches 24 and 26 therein. The fixed resistance RX is electrically connected at a first side to over-temperature sensor 32, illustrated as resistance RF in the equivalent electrical schematic diagram of Fig. 2B. The second side of fixed resistance RX is connected to the phase line 12. The first end of the resistance RF (the sensor 32) is connected to the resistance Rx. The signal on line 35 (the sense wire) at the point of connection 36 between resistance RF and resistance RX is referred to as the sensor signal. The second end of resistance RF (the sensor 32) is connected to the neutral line 14. The first end of resistance RF is also electrically connected to a capacitor C l and an anode end of the diode Dl. Cathode end of diode Dl is electrically connected to the cathode of zener diode Zl . The anode end of zener diode Zl is electrically connected to a secondcapacitor C2 and a gate of a silicon controlled rectifier SCR1. By switching the SCR1 on/off, the state of contact switches 24 and 26 and therefore, the conductive state of the cord 10, is controlled. The resistance of resistance RF varies as a function of temperature, thereby varying the sensor signal and the control signal from zener diode Zl to the gate of the SCR1.
Capacitor C2 has a value of .01 microfarads and capacitor Cl has a value of 0.1 microfarads. The capacitor C l is preferably mounted at the plug end of the fiber sensor 32 and provides noise i.lllllllll;l~y.
Fig. 2B is an electrical schematic diagram for the physical schematic diagram for the embodiment of Fig. 2A. Fig. 2B illustrates the sensor 32 as a resistance RF across the capacitor Cl, connected between the fixed resistance RX and the neutral line.
In yet another embodiment of the present invention, the power cord may include ground fault protection c~cuilly and/or over voltage protection. Fig. 3 is an electrical schematic diagram which illustrates another embodiment of a power cord employing the present invention. Ground fault and/or over voltage sensor 39 in conjunction with GFCI
IC 38 detects ground faults and/or over voltage conditions. The ground fault or over voltage sensor 39 may be a toroidal core with a coil winding, for example. The ends of the coil winding may be input at pins 2 and 3 of the GFCI IC 38. The GFCI IC 38 detects an undesirable ground fault condition based upon the signals from the coil winding.
GFCI IC 38 outputs a ground fault control signal from pin 1 when a ground fault and/or over voltage condition is detected. The ground fault control signal from pin 1 is input to control circuit 30'. The GFCI IC 38 can be any GFCI such as a National Semi Conductor Inc. (NSI) integrated circuit LM 1851 which is commercially available. Further, a Motorola circuit MC3426, which can be purchased, may be used with simple modifications. The IC cir.iuil~ can be used in the circuit in accordance with known requirements of the chosen IC.
The silicon controlled rectifier SCRl triggers when a ground fault is sensed. The SCR1 also triggers if an over-voltage condition is sensed. As illustrated in Fig. 3, the SCRl further triggers when over-temperature is detected by sensor 32. By switching SCRl on/off, the state of contact switches 24 and 26 and therefore, the conductive state of the cord, is controlled. The resistance of resistance RF (sensor 32) varies as a function of temperature, thereby varying both of the sensor signal at connection point 36 and the control signal from zener diode Z 1 to the gate of the SCR1. Additionally, the ground fault control signal from pin 1 controls the gate of the SCR1 to render the cord non-conductive when a ground fault or over voltage condition is detected. Capacitor C l has a value of 0.1 microfarads. Control circuit 30' is similar to control circuit 30 of Figs. 2A
and B. Further, the housing 34' of Fig.3 is similar to the housing 34 of Figs. 2A and B.
Housing 34 of Figs. 2A and B and housing 34' of Fig.3 are the plug of a power cord and/or extension cord. ~lt~ hvely, the housing can be the plug of an appliance cord.
Fig. 4 is a physical schem~hc diagram of another embodiment of the invention.
The embodiment of a Fig. 4 is similar in all respects to the embodiment of Fig. 2A, however, the cord includes multiple sensors 32 in series, rather than a continuous long fiber along the length of a cord. As illustrated there are n sensors in series along a length of the cord. The embodiment of Fig. 4 may be employed to detect over-temperatureconditions along a length of cord. Figs. 5A and 5B show an electrical schematic diagram with the resistances RF of the multiple sensors illushrated in series. As illustrated in Fig.
5A, there is no over-temperature condition present. When one of these sensors gets hot its resistance increases as illustrated in Fig. 5B. As illustrated in Fig. 5B sensor 323 is subject to an over-temperature condition and the resistance of sensor 323 has increased to I OOORF
The embodiments of the invention as illustrated in Figs. 2A and 4 may be used todetect an over-temperature in a load by locating the sensors 321-32n within a load device.
The embodiment of Fig. 4 may be further modified to include a ground fault detector and ground fault circuit intellu~lel and/or an over voltage detector and an over voltage circuit intellul)lel as illustrated in Fig.3.
Fig. 6A shows a portion of a power cord 41 of the present invention, including male plug 42. Male plug 42 includes phase, neutral and ground blades 44, 46 and 48, respectively, which are internally connected via termin~ 16 and 18 to circuit 30. The conductive cable portion 40 of cord 41 includes phase, neutral and ground conductors (not shown), as well as sense wire 35 which connects to an over-temperature sensor 32 further down the cable portion. The cable portion may end with a female connector (i.e., receptacle) or may end directly at a load to which the cord 41 is hard wired. The load may be an appliance.
The temperature detection means may include a thermocouple wire or a thermo cutoff device through which the conductive path of the cord/cable passes. Preferably, the temperature detection means includes a thermo sensitive m~tçri~l which displays a positive temperature coefficient of resistance. The resistance may be measured at any point in the power cord length, but prefel~bly close to the location of the inl~llul)ler. In power cord applications, a detection means in a form of a wire could be extended from an IGFCI mounted in the conductive path into the device or appliance being powered. In this m~nner, the wire could be routed throughout the equipment to be in tllerm~l contact with any expected hot spots.
Fig. 6B shows an electrical cable 41 electrically hardwired to a load 50, wherein sense wire 35 extends throughout the load. At particular potential hotspots or sensitive areas of the load, over-temperature sensors 32 are located. If an over-temperature condition is detected somewhere within the load 50, a signal acknowledging the same is realized at control circuit 30" which acts to open contact switches 24 and 26, cutting off power to the load.
Fig. 6C shows an electrical cable 41 electrically hardwired to a load 50, wherein the sensor 32 extends throughout the load. The sensor 32 is a long continuous fiber as illustrated in Fig. 2A. The connections to the neutral line 14 are not shown in Fig. 6C for ease of illustration. The sensor 32 is positioned adjacent potential hotspots or sensitive areas. If an over-temperature condition is detected somewhere within the load 50, a signal acknowledging the same is realized at central circuit 30" which acts to open contact switches 24 and 26 cutting off power to the load.
Fig. 6D is similar to Fig. 6B but illustrates the cord powering the motor 49 of the load 50.
Fig. 6E is similar to Fig. 6C but illustrates the cord powering the motor 49 of the load 50.
Fig. 6F illustrates an embodiment of the invention where the cord is the cord attached to an appliance as opposed to a separate extension cord.
Fig. 7A shows a cross-section of a portion 51 of an over-temperatu-re protected extension cord with temperature sensor. The cord has an outer jacket 58. Shown therein are two insulated power conductors 52 and 56 and an insulated temperature sensor fiber 55. Insulation is shown as numerals 53, 57 and 54. In case any part of the extension cord overheats, the resistance of the temperature sensitive material of sensor fiber 55 changes.
As discussed above, the resistance of the temperature sensitive material is measured at the end of the extension cord pl oximate an illlell upler ci-rcuit similar to that used in an IDCI.
The inl~ll upler circuit disconnects power through the cord 51 at over-temperature detection, preferably before heat damage to the cord is realized.
Fig. 7B illustrates another embodiment of a portion 51' of an over-temperature protected extension cord with temperature sensor. -In the cross-section of portion 51' insulated conductors 52 and 56 are illustrated with the temperature sensitive material 55' molded around them. The jacket 58 is molded about the encased conductors and temperature sensitive molding. Fig. 7C illustrates a further embodiment of a portion 51"
of an over-temperature protected extension cord with temperature sensor. Shown therein are two insulated power conductors 52 and 56 and temperature sensor 55" as illustrated in Fig. 7B. In Fig. 7C the temperature sensor portion 55" and another insulated conductor 59 are molded in the outer jacket 58. The conductor 59 may be the ground wire. Fig. 7D
illustrates a further embodiment of a portion 51"' of an over-temperature protected extension cord with temperature sensor. Shown therein are multiple, for example three, insulated power conductors 59, 61 and 63 and temperature sensor portion 55"' which oullds the in~nl~te~l power conductors 52 and 56 molded inside the outer jacket 58.
One of the features of the electrical power cord or cable over-temperature protection ability of the present invention is its use of temperature sensitive material.
More particularly, the temperature sensitive material has a positive temperaturecoefficient of resistance. A prototype of an extension cord of this invention was built I1tili~ing a m~teriAl D.O.T.S. (formerly D.O.S.) m~nllf~ctured by Raychem Corporation, of Menlo Park, California, similar to m~tçri~l found in Raychem heat tracing tape which takes the form of a plastic web (fiber) of positive temperature coefficient material, separated by copper leads. The fiber is a carbon fiber. Fig. 8 shows a plot of log norm~ ed resistance over temperature for a forml-l~tion of this m~teri~l The material is a non-linear resistance m~t~ri~l With a fiber length of 6 inches the temperatureresistance characteristic is as follows: at 25~ and 60~ Centigrade the resistance of the fiber is found to be R. At 110~C, the resistance rises to 1000R. The operationaltemperature range is -50 to 125~C. The fiber is easily interfaced with brass contacts.
Additional plots of resistance over temperature for other samples of material are illustrated in Figs. 9-12. Depending upon the use of the cord, a different trip point temperature at which the resistance suddenly changes may be desirable. For example, for a high gauge wire which is thin in diameter, it may be desirable to designate a lower temperature as the temperature trip point. A formulation of the temperature sensitive material which changes resistance at a low temperature may be chosen. For low gauge wires a higher temperature trip point may be desired. Accordingly, a fonnlll~tion of the temperature sensitive material with a high trip point may be chosen.
Raychem Corporation designated D.O.T.S. material with albill~ily assigned colors for varying trip point temperatures are as follow:
Approximate ~orm~ hon Threshold Temperature Black Material 80~C
Blue Material 120~C
Brown l~tçri~l 135~C
Fig. 9 illustrates a plot of resistance over temperature for the Brown formulation.
Fig. 10 illustrates a plot of resistance over temperature for the Blue form~ hon. Fig. 11 illustrates a plot of resistance over temperature for the Black formlll~tion.
Fig. 12 illustrates plots of resistance over temperature for three different form~ tions of temperature sensitive m~teri~l having somewhat dirrelellt tlip points with Raychem designated forml1l~hon numbers. The plot for Formlll~hon 10563-09-2 is also shown in Fig. 8.
A temperature sensitive material is chosen with the a~propliate temperature trippoint for the application in order to designate a prede~e,ll~ined temperature value which is considered an excessive temperature for safety reasons.
Although the invention has been described with reference to the prerelled embodiments, it will be apparent to one skilled in the art that variations and modifications are collteml.lated within the spirit and scope of the invention. The drawings and descriptions of the prefel,ed embodiments are made by way of example rather than to limit the scope of the invention, and it is intended to cover within the scope and spirit of the invention all such changes and modifications. For example, any number of power conductors may be included within the electrical cord of the present invention. Further, electrical cords which are not power cords may employ a temperature sensor and means for inl~ll uplillg conductivity of the cord in the event of over-temperature. For example, speaker wire may be provided with over-temperature protection. The temperature sensing means may be a temperature sensitive material such as a fiber with a positive temperah~re coefficient. As set forth above, such a fiber exhibits changes in resistance in response to changes in temperature.
CORD WITH OVER-TEMPERATURE PROTECTION
FIELD OF THE INVENTION
The present invention relates to electrical cords, and more particularly to electrical cords or cables which include safety protection.
BACKGROUND OF THE INVENTION
Electrical cords including electrical power cords, e.g., extension cords, are found in some form everywhere electrical power is utilized. While safe as a general rule, the conductor or current carrying element which comprises the power cord may generate substantial heat under certain circumstances, leading to a dangerous condition. For example, if a current flowing through a power cord causes a heat rise which exceeds a certain temperature, a change in the characteristics of the insulation surrounding the conductor can occur. This change could lead to brittleness, fl~king and breaking of the insulation which could result in exposure of conductor portions. Arcing from theexposed conductors could lead to fire or injury to people coming into contact with the heat-damaged power cord.
Current flowing through a power cord may cause a temperature rise to an extent where insulation melting and/or actual ~lre occurs. This is especially so where cords are coiled or several cords are gathered in a limited space. Numerous fires are attributed to malfunctioning and/or overheated extension cords. A method and/or apparatus which prevents excessive overheating in electrical extension cords, electrical power cords, power strips or cord sets, etc., would be well received for both in-home use and industry.
OBJECTS AND SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an electrical extension and/or power cord which overcomes the above-described shortcomings of the prior art.
It is another object of the present invention to provide an electrical extensionand/or power cord which will render itself non-conductive upon the detection of an over-temperature condition.
It is another object of the present invention to provide an electrical power and/or extension cord which includes a temperature detector and a circuit illlell u~l device which controls the conductivity of the cord in accordance with a signal provided by the temperature detector.
It is a further object of the present invention to provide an electrical power and/or extension cord which provides over-temperature and ground fault protection.
It is yet a further object of the present invention to provide an electrical power and/or extension cord which includes a temperature detector, a ground fault detector, and a circuit illt~ll u~t device which controls the conductivity of the cord to render the cord non-conductive when an over-temperature condition, a ground fault condition or an over voltage condition is detected.
It is still a further object of the present invention to provide over-temperature protection for an electrical power and/or extension cord which is inexpensive and easily m~mlf~ctured.
It is an additional object of the present invention to provide a cable for sensing over-temperature areas of a load.
It is a further additional object of the present invention to provide an inlellul)l circuit that renders a cord non-conductive when over-temperature of a load is detected.
lt is an object of the present invention to provide a method of protecting an electrical cord from over-te~ e,~ e conditions.
It is a further object of the present invention to provide a cable with over-temperature protection employing a temperature sensitive material that responds to changes in temperature by changes in its resistance.
It is still a further object of the present invention to provide a method of sensing over-temperatures in a load.
To that end, an electrical cord such as an electrical power and/or extension cord which includes over-temperature protection is provided hereby. These and other objects of the invention are accomplished by providing an electrical cord inclll-ling over-temperature protection, comprising an electrical conductor surrounded by an insulating material; over-temperature sensor means disposed plo~imate the electrical conductor for detecting over-temperatures and generating a sensor control signal in accordance thereto;
and illte~lul)t means electrically responsive to the sensor control signal disposed within the conductive path formed by the electrical conductor for defining a state of conductivity of the electrical conductor in accordance with the sensor control signal. Additionally, there is provided a method of protecting an electrical cord from over-temperature conditions, comprising: placing an over-temperature sensor proximate an electrical conductor ~ulloullded by an insulating material; detecting over-temperatures with the sensor; generating a sensor control signal by the sensor; and il~te~ g conductivity of the electrical conductor in response to the sensor control signal when an over-temperature is detected.
In one embodiment of the invention there is provided a cable providing over-temperature protection comprising: a conductor; a sense wire; temperature sensitive material disposed adjacent the conductor and sense wire; the temperature sensitive material responding to temperature changes by change in resistance; measuring means for measuring changes in resistance to detect a change in temperature and for generating a temperature control signal when the change in temperature exceeds a predele~ ed value; and intellul~l means responsive to the temperature control signal for inlell.lpling electrical power to a load in accordance with the temperature control signal.
Further, a method of providing over-temperature protection is disclosed herein.
Another embodiment of the invention provides a cable for providing over-temperature protection for a load, comprising: over-temperature sensing means for detecting over-temperatures in a load and for generating a sensor control signal in accordance thereto; and a sense wire carrying the sensor control signal connecting the sensing means to inlellupl means; the il~lellu~ g means electrically responsive to the sensor control signal for il~lell u~ g electrical power to the load in accordance with the temperature control signal; wherein the over-temperature sensing means comprises a temperature sensitive m~teri~l that undergoes a change in resistance in response to a change in temperature.
The invention further provides a method of providing over-temperature protectionfor a load, comprising: placing over-temperature sensing means in a load; detecting over-temperatures in the load with the over-temperature sensing means; generating a sensor control signal by the over-temperature sensing means; and inlell u~ g electrical power to the load in accordance with the sensor control signal; wherein the over-temperature sensing means comprises a temperature sensitive material that undergoes a change in resistance in response to a change in temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by way of example and not limitation in the figures of the accolllp~ying drawings in which like references denote like and corresponding parts and in which:
Fig. lA is a schem~hc diagram of an electrical power cord with over-temperature protection in accordance with the present invention;
Fig. lB is a schematic diagram of a section of cable of the embodiment of the present invention illustrated in Fig. lA;
Fig. 2A is a physical schematic diagram illustrating the cir.;u,lly of the control circuitofFig. lA;
Fig. 2B is an electrical schematic diagram illustrating the cir.;u-lly of the control circuitofFig. lA;
Fig. 3 is a schematic diagram showing the ci~iL-y of a second embodiment of the present invention with ground fault protection;
Fig. 4 is a physical sçhem~hc diagram showing the c~.iuiLIy of the control circuit for a third embodiment of the present invention;
Fig. SA is an electrical diagram showing the resistance values of the sensor fibers of the embodiment of the present invention shown in Fig. 4 before an over temperature condition;
Fig. 5B is an electrical diagram showing the resistance values of the sensor fibers of the embodiment of the present invention shown in Fig. 4 after an over temperature condition;
Fig. 6A is a schematic diagram of a fourth embodiment of the present invention for an extension cord;
Fig. 6B is a schematic diagram of a flfth embodiment of the present invention for sensing over-temperatures in a load with multiple sensors as in Fig. 4;
Fig. 6C is a schematic diagram of a sixth embodiment of the present invention for sensing over-temperatures in a load with a long continuous sensor as in Fig. 2A;Fig. 6D is a schematic diagram of a seventh embodiment of the present invention for sensing over-temperatures in a load with multiple sensors where the power cord provides power to the load;
Fig. 6E is a schematic diagram of an eighth embodiment of the present invention for sensing over-temperatures in a load with a long continuous sensor where the power cord provides power to the load;
Fig. 6F is a schem~tic diagram of a ninth embodiment of the present invention for a power cord of an appliance;
Figs. 7A - 7D are cross-sectional views of embodiments of electrical cords with temperature detecting sensors in accordance with the present invention; and Figs. 8 - 12 are plots of resistance over temperature for form~ tions of temperature sensitive materials for lltili7.~tion in the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Operation of a first embodiment of the power cable with over-temperature protection of the present invention will now be described with lererellce to the drawings in which like references denote like and corresponding parts. In Fig. lA cord 10 is shown comprising a phase conductor, and a neutral conductor, 12 and 14, respectively, for connection to a source of power via t~rmin~ 16 and 18 and to tçrmin~l~ of a plug or load 20 and 22, respectively. The conductors and tçrmin~l~ may be implemented in any manner known to those skilled in the art for creating a conductive path through a power cable.
Cord 10 also includes a control circuit 30 for controlling conduction of currentthrough a relay coil 28. Relay coil 28 is illustrated as having inductance L. Relay coil 28 controls the state of contact switches 24 and 26, which in turn controls the conductive state of the power cord. An over-temperature sensor 32 detects a change in temperature at its location in the power cord and generates a sensor signal on line 35 in accordance with the temperature. The control circuit 30 is responsive to the sensor signal. The over-temperature sensor 32 may be a continuous fiber extending nearly the length of the cord 10.
Fig. lB shows an enlarged view of temperature sensor 32 and its interconnection with conductors 12 and 14 of cord 10. The over-temperature sensor is prefel~bly comprised of a m~teri~l which displays a positive temperature coefficient. That is, the resistance of the sensor material increases with increasing temperature. One side of sensor 32 is electrically connected to the neutral conductor 14 via wire 31. The other side of sensor 32 is cormected to the wire 35. A sensor signal on wire 35 (the sense wire) is input to the control circuit 30. Because the voltage across the sensor material is constant, a change in temperature with its concon~ilanl change in resistance will define a current (or voltage) change through the sensor. The sensor signal is generated thereby.
Fig. 2A is a physical schem~tic diagram showing in detail one embodiment of a control circuit 30 and its connection to conductors 12 and 14 and the over-temperature sensor 32 which may be utilized for the present invention. Control circuit 30 is located within housing 34 which also holds a fixed resistance RX and relay coil 28 as well as switches 24 and 26 therein. The fixed resistance RX is electrically connected at a first side to over-temperature sensor 32, illustrated as resistance RF in the equivalent electrical schematic diagram of Fig. 2B. The second side of fixed resistance RX is connected to the phase line 12. The first end of the resistance RF (the sensor 32) is connected to the resistance Rx. The signal on line 35 (the sense wire) at the point of connection 36 between resistance RF and resistance RX is referred to as the sensor signal. The second end of resistance RF (the sensor 32) is connected to the neutral line 14. The first end of resistance RF is also electrically connected to a capacitor C l and an anode end of the diode Dl. Cathode end of diode Dl is electrically connected to the cathode of zener diode Zl . The anode end of zener diode Zl is electrically connected to a secondcapacitor C2 and a gate of a silicon controlled rectifier SCR1. By switching the SCR1 on/off, the state of contact switches 24 and 26 and therefore, the conductive state of the cord 10, is controlled. The resistance of resistance RF varies as a function of temperature, thereby varying the sensor signal and the control signal from zener diode Zl to the gate of the SCR1.
Capacitor C2 has a value of .01 microfarads and capacitor Cl has a value of 0.1 microfarads. The capacitor C l is preferably mounted at the plug end of the fiber sensor 32 and provides noise i.lllllllll;l~y.
Fig. 2B is an electrical schematic diagram for the physical schematic diagram for the embodiment of Fig. 2A. Fig. 2B illustrates the sensor 32 as a resistance RF across the capacitor Cl, connected between the fixed resistance RX and the neutral line.
In yet another embodiment of the present invention, the power cord may include ground fault protection c~cuilly and/or over voltage protection. Fig. 3 is an electrical schematic diagram which illustrates another embodiment of a power cord employing the present invention. Ground fault and/or over voltage sensor 39 in conjunction with GFCI
IC 38 detects ground faults and/or over voltage conditions. The ground fault or over voltage sensor 39 may be a toroidal core with a coil winding, for example. The ends of the coil winding may be input at pins 2 and 3 of the GFCI IC 38. The GFCI IC 38 detects an undesirable ground fault condition based upon the signals from the coil winding.
GFCI IC 38 outputs a ground fault control signal from pin 1 when a ground fault and/or over voltage condition is detected. The ground fault control signal from pin 1 is input to control circuit 30'. The GFCI IC 38 can be any GFCI such as a National Semi Conductor Inc. (NSI) integrated circuit LM 1851 which is commercially available. Further, a Motorola circuit MC3426, which can be purchased, may be used with simple modifications. The IC cir.iuil~ can be used in the circuit in accordance with known requirements of the chosen IC.
The silicon controlled rectifier SCRl triggers when a ground fault is sensed. The SCR1 also triggers if an over-voltage condition is sensed. As illustrated in Fig. 3, the SCRl further triggers when over-temperature is detected by sensor 32. By switching SCRl on/off, the state of contact switches 24 and 26 and therefore, the conductive state of the cord, is controlled. The resistance of resistance RF (sensor 32) varies as a function of temperature, thereby varying both of the sensor signal at connection point 36 and the control signal from zener diode Z 1 to the gate of the SCR1. Additionally, the ground fault control signal from pin 1 controls the gate of the SCR1 to render the cord non-conductive when a ground fault or over voltage condition is detected. Capacitor C l has a value of 0.1 microfarads. Control circuit 30' is similar to control circuit 30 of Figs. 2A
and B. Further, the housing 34' of Fig.3 is similar to the housing 34 of Figs. 2A and B.
Housing 34 of Figs. 2A and B and housing 34' of Fig.3 are the plug of a power cord and/or extension cord. ~lt~ hvely, the housing can be the plug of an appliance cord.
Fig. 4 is a physical schem~hc diagram of another embodiment of the invention.
The embodiment of a Fig. 4 is similar in all respects to the embodiment of Fig. 2A, however, the cord includes multiple sensors 32 in series, rather than a continuous long fiber along the length of a cord. As illustrated there are n sensors in series along a length of the cord. The embodiment of Fig. 4 may be employed to detect over-temperatureconditions along a length of cord. Figs. 5A and 5B show an electrical schematic diagram with the resistances RF of the multiple sensors illushrated in series. As illustrated in Fig.
5A, there is no over-temperature condition present. When one of these sensors gets hot its resistance increases as illustrated in Fig. 5B. As illustrated in Fig. 5B sensor 323 is subject to an over-temperature condition and the resistance of sensor 323 has increased to I OOORF
The embodiments of the invention as illustrated in Figs. 2A and 4 may be used todetect an over-temperature in a load by locating the sensors 321-32n within a load device.
The embodiment of Fig. 4 may be further modified to include a ground fault detector and ground fault circuit intellu~lel and/or an over voltage detector and an over voltage circuit intellul)lel as illustrated in Fig.3.
Fig. 6A shows a portion of a power cord 41 of the present invention, including male plug 42. Male plug 42 includes phase, neutral and ground blades 44, 46 and 48, respectively, which are internally connected via termin~ 16 and 18 to circuit 30. The conductive cable portion 40 of cord 41 includes phase, neutral and ground conductors (not shown), as well as sense wire 35 which connects to an over-temperature sensor 32 further down the cable portion. The cable portion may end with a female connector (i.e., receptacle) or may end directly at a load to which the cord 41 is hard wired. The load may be an appliance.
The temperature detection means may include a thermocouple wire or a thermo cutoff device through which the conductive path of the cord/cable passes. Preferably, the temperature detection means includes a thermo sensitive m~tçri~l which displays a positive temperature coefficient of resistance. The resistance may be measured at any point in the power cord length, but prefel~bly close to the location of the inl~llul)ler. In power cord applications, a detection means in a form of a wire could be extended from an IGFCI mounted in the conductive path into the device or appliance being powered. In this m~nner, the wire could be routed throughout the equipment to be in tllerm~l contact with any expected hot spots.
Fig. 6B shows an electrical cable 41 electrically hardwired to a load 50, wherein sense wire 35 extends throughout the load. At particular potential hotspots or sensitive areas of the load, over-temperature sensors 32 are located. If an over-temperature condition is detected somewhere within the load 50, a signal acknowledging the same is realized at control circuit 30" which acts to open contact switches 24 and 26, cutting off power to the load.
Fig. 6C shows an electrical cable 41 electrically hardwired to a load 50, wherein the sensor 32 extends throughout the load. The sensor 32 is a long continuous fiber as illustrated in Fig. 2A. The connections to the neutral line 14 are not shown in Fig. 6C for ease of illustration. The sensor 32 is positioned adjacent potential hotspots or sensitive areas. If an over-temperature condition is detected somewhere within the load 50, a signal acknowledging the same is realized at central circuit 30" which acts to open contact switches 24 and 26 cutting off power to the load.
Fig. 6D is similar to Fig. 6B but illustrates the cord powering the motor 49 of the load 50.
Fig. 6E is similar to Fig. 6C but illustrates the cord powering the motor 49 of the load 50.
Fig. 6F illustrates an embodiment of the invention where the cord is the cord attached to an appliance as opposed to a separate extension cord.
Fig. 7A shows a cross-section of a portion 51 of an over-temperatu-re protected extension cord with temperature sensor. The cord has an outer jacket 58. Shown therein are two insulated power conductors 52 and 56 and an insulated temperature sensor fiber 55. Insulation is shown as numerals 53, 57 and 54. In case any part of the extension cord overheats, the resistance of the temperature sensitive material of sensor fiber 55 changes.
As discussed above, the resistance of the temperature sensitive material is measured at the end of the extension cord pl oximate an illlell upler ci-rcuit similar to that used in an IDCI.
The inl~ll upler circuit disconnects power through the cord 51 at over-temperature detection, preferably before heat damage to the cord is realized.
Fig. 7B illustrates another embodiment of a portion 51' of an over-temperature protected extension cord with temperature sensor. -In the cross-section of portion 51' insulated conductors 52 and 56 are illustrated with the temperature sensitive material 55' molded around them. The jacket 58 is molded about the encased conductors and temperature sensitive molding. Fig. 7C illustrates a further embodiment of a portion 51"
of an over-temperature protected extension cord with temperature sensor. Shown therein are two insulated power conductors 52 and 56 and temperature sensor 55" as illustrated in Fig. 7B. In Fig. 7C the temperature sensor portion 55" and another insulated conductor 59 are molded in the outer jacket 58. The conductor 59 may be the ground wire. Fig. 7D
illustrates a further embodiment of a portion 51"' of an over-temperature protected extension cord with temperature sensor. Shown therein are multiple, for example three, insulated power conductors 59, 61 and 63 and temperature sensor portion 55"' which oullds the in~nl~te~l power conductors 52 and 56 molded inside the outer jacket 58.
One of the features of the electrical power cord or cable over-temperature protection ability of the present invention is its use of temperature sensitive material.
More particularly, the temperature sensitive material has a positive temperaturecoefficient of resistance. A prototype of an extension cord of this invention was built I1tili~ing a m~teriAl D.O.T.S. (formerly D.O.S.) m~nllf~ctured by Raychem Corporation, of Menlo Park, California, similar to m~tçri~l found in Raychem heat tracing tape which takes the form of a plastic web (fiber) of positive temperature coefficient material, separated by copper leads. The fiber is a carbon fiber. Fig. 8 shows a plot of log norm~ ed resistance over temperature for a forml-l~tion of this m~teri~l The material is a non-linear resistance m~t~ri~l With a fiber length of 6 inches the temperatureresistance characteristic is as follows: at 25~ and 60~ Centigrade the resistance of the fiber is found to be R. At 110~C, the resistance rises to 1000R. The operationaltemperature range is -50 to 125~C. The fiber is easily interfaced with brass contacts.
Additional plots of resistance over temperature for other samples of material are illustrated in Figs. 9-12. Depending upon the use of the cord, a different trip point temperature at which the resistance suddenly changes may be desirable. For example, for a high gauge wire which is thin in diameter, it may be desirable to designate a lower temperature as the temperature trip point. A formulation of the temperature sensitive material which changes resistance at a low temperature may be chosen. For low gauge wires a higher temperature trip point may be desired. Accordingly, a fonnlll~tion of the temperature sensitive material with a high trip point may be chosen.
Raychem Corporation designated D.O.T.S. material with albill~ily assigned colors for varying trip point temperatures are as follow:
Approximate ~orm~ hon Threshold Temperature Black Material 80~C
Blue Material 120~C
Brown l~tçri~l 135~C
Fig. 9 illustrates a plot of resistance over temperature for the Brown formulation.
Fig. 10 illustrates a plot of resistance over temperature for the Blue form~ hon. Fig. 11 illustrates a plot of resistance over temperature for the Black formlll~tion.
Fig. 12 illustrates plots of resistance over temperature for three different form~ tions of temperature sensitive m~teri~l having somewhat dirrelellt tlip points with Raychem designated forml1l~hon numbers. The plot for Formlll~hon 10563-09-2 is also shown in Fig. 8.
A temperature sensitive material is chosen with the a~propliate temperature trippoint for the application in order to designate a prede~e,ll~ined temperature value which is considered an excessive temperature for safety reasons.
Although the invention has been described with reference to the prerelled embodiments, it will be apparent to one skilled in the art that variations and modifications are collteml.lated within the spirit and scope of the invention. The drawings and descriptions of the prefel,ed embodiments are made by way of example rather than to limit the scope of the invention, and it is intended to cover within the scope and spirit of the invention all such changes and modifications. For example, any number of power conductors may be included within the electrical cord of the present invention. Further, electrical cords which are not power cords may employ a temperature sensor and means for inl~ll uplillg conductivity of the cord in the event of over-temperature. For example, speaker wire may be provided with over-temperature protection. The temperature sensing means may be a temperature sensitive material such as a fiber with a positive temperah~re coefficient. As set forth above, such a fiber exhibits changes in resistance in response to changes in temperature.
Claims (29)
1. An electrical cord including over-temperature protection, comprising:
an electrical conductor surrounded by an insulating material;
over-temperature sensor means disposed proximate said electrical conductor for detecting over-temperatures and generating a sensor control signal in accordance thereto; and interrupt means electrically responsive to said sensor control signal disposed within the conductive path formed by said electrical conductor for defining a state of conductivity of said electrical conductor in accordance with said sensor control signal.
an electrical conductor surrounded by an insulating material;
over-temperature sensor means disposed proximate said electrical conductor for detecting over-temperatures and generating a sensor control signal in accordance thereto; and interrupt means electrically responsive to said sensor control signal disposed within the conductive path formed by said electrical conductor for defining a state of conductivity of said electrical conductor in accordance with said sensor control signal.
2. The electrical cord recited in Claim 1, wherein said electrical cord is a power cord.
3. The electrical cord recited in Claim 1, wherein there are plural electrical conductors each surrounded by an insulating material.
4. The electrical cord recited in Claim 1, wherein said over-temperature sensor means comprises a temperature sensitive material.
5. The electrical cord recited in Claim 4, wherein said temperature sensitive material undergoes a change in resistance in response to a change in temperature.
6. The electrical cord recited in Claim 5, wherein said temperature sensitive material has a positive temperature coefficient.
7. The electrical cord recited in Claim 1, wherein said over-temperature sensor means comprises a temperature sensitive fiber.
8. The electrical cord recited in Claim 7, wherein said fiber extends nearly the length of said electrical cord.
9. The electrical cord recited in Claim 1, further comprising ground fault sensor means for detecting ground faults and over-voltage conditions and for generating a ground fault control signal in accordance thereto.
10. The electrical cord recited in Claim 9, wherein said interrupt means is electrically responsive to said ground fault control signal and defines a state of conductivity of said electrical conductor in accordance with said ground fault control signal aswell as said sensor control signal.
11. The electrical cord recited in Claim 1, wherein said over-temperature sensor means comprises multiple sensors connected in series.
12. A method of protecting an electrical cord from over-temperature conditions, comprising the steps of:
placing an over-temperature sensor proximate an electrical conductor surrounded by an insulating material;
detecting over-temperatures with said sensor;
generating a sensor control signal by said sensor; and interrupting conductivity of said electrical conductor in response to said sensor control signal when an over-temperature is detected.
placing an over-temperature sensor proximate an electrical conductor surrounded by an insulating material;
detecting over-temperatures with said sensor;
generating a sensor control signal by said sensor; and interrupting conductivity of said electrical conductor in response to said sensor control signal when an over-temperature is detected.
13. The method recited in Claim 12, wherein said over-temperature sensor comprises a temperature sensitive material.
14. The method recited in Claim 12, wherein said temperature sensitive material undergoes a change in resistance in response to a change in temperature.
15. The method recited in Claim 14, wherein said temperature sensitive material has a positive temperature coefficient.
16. The method recited in Claim 12, wherein said over-temperature sensor means comprises a temperature sensitive fiber.
17. The method recited in Claim 16, wherein said fiber extends nearly the length of said electrical cord.
18. The method recited in Claim 12, wherein said over-temperature sensor means comprises multiple sensors connected in series.
19. The method of Claim 12, further comprising the steps of:
detecting ground fault and over voltage conditions with a ground fault sensor;
generating a ground fault control signal by said ground fault sensor;
interrupting conductivity of said electrical conductor in response by said ground fault control signal when at least one of a ground fault and an over-voltage condition is detected.
detecting ground fault and over voltage conditions with a ground fault sensor;
generating a ground fault control signal by said ground fault sensor;
interrupting conductivity of said electrical conductor in response by said ground fault control signal when at least one of a ground fault and an over-voltage condition is detected.
20. A cable providing over-temperature protection comprising:
a conductor;
a sense wire;
temperature sensitive material disposed adjacent said conductor and sense wire, said temperature sensitive material responding to temperature changes by changes in resistance;
measuring means for measuring changes in resistance to detect a change in temperature and for generating a temperature control signal when said change in temperature exceeds a predetermined value; and interrupt means responsive to said temperature control signal for interrupting electrical power to a load in accordance with said temperature control signal.
a conductor;
a sense wire;
temperature sensitive material disposed adjacent said conductor and sense wire, said temperature sensitive material responding to temperature changes by changes in resistance;
measuring means for measuring changes in resistance to detect a change in temperature and for generating a temperature control signal when said change in temperature exceeds a predetermined value; and interrupt means responsive to said temperature control signal for interrupting electrical power to a load in accordance with said temperature control signal.
21. A method of providing over-temperature protection, comprising the steps of:
placing a temperature sensitive material adjacent a conductor and a sense wire within a cable, wherein said temperature sensitive material responds to temperature changes by changing its resistance;
measuring changes in resistance to detect a change in temperature;
generating a temperature control signal when said change in temperature exceeds a predetermined value; and interrupting electrical power to a load in accordance with said temperature control signal.
placing a temperature sensitive material adjacent a conductor and a sense wire within a cable, wherein said temperature sensitive material responds to temperature changes by changing its resistance;
measuring changes in resistance to detect a change in temperature;
generating a temperature control signal when said change in temperature exceeds a predetermined value; and interrupting electrical power to a load in accordance with said temperature control signal.
22. A cable for providing over-temperature protection for a load, comprising:
over-temperature sensing means for detecting over-temperatures in a load and for generating a sensor control signal in accordance thereto; and a sense wire carrying said sensor control signal and connecting said sensing means to interrupting means;
said interrupt means electrically responsive to said sensor control signal for interrupting electrical power to said load in accordance with said temperature control signal;
wherein said over-temperature sensing means comprises a temperature sensitive material that undergoes a change in resistance in response to a change in temperature.
over-temperature sensing means for detecting over-temperatures in a load and for generating a sensor control signal in accordance thereto; and a sense wire carrying said sensor control signal and connecting said sensing means to interrupting means;
said interrupt means electrically responsive to said sensor control signal for interrupting electrical power to said load in accordance with said temperature control signal;
wherein said over-temperature sensing means comprises a temperature sensitive material that undergoes a change in resistance in response to a change in temperature.
23. The cable recited in Claim 22, wherein said over-temperature sensing means is located within said load.
24. The cable recited in Claim 22, wherein said over-temperature sensing means is a long fiber nearly extending the length of the cable.
25. The cable recited in Claim 22, wherein said over-temperature sensing means comprises multiple sensors connected in series.
26. A method of providing over-temperature protection for a load, comprising the steps of:
placing over-temperature sensing means in said load;
detecting over-temperatures in said load with said over-temperature sensing means;
generating a sensor control signal by said over-temperature sensing means;
and interrupting electrical power to said load in accordance with said sensor control signal;
wherein said over-temperature sensing means comprises a temperature sensitive material that undergoes a change in resistance in response to a change in temperature.
placing over-temperature sensing means in said load;
detecting over-temperatures in said load with said over-temperature sensing means;
generating a sensor control signal by said over-temperature sensing means;
and interrupting electrical power to said load in accordance with said sensor control signal;
wherein said over-temperature sensing means comprises a temperature sensitive material that undergoes a change in resistance in response to a change in temperature.
27. The method recited in Claim 26, wherein said over-temperature sensing means comprises multiple sensors, and further comprising connecting said multiple sensors in series.
28. The method recited in Claim 26, wherein said over-temperature sensing means is part of a cable that includes a sense wire for carrying said sensor control signal.
29. The method recited in Claim 26, wherein said over-temperature sensing means comprises a long fiber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US87272697A | 1997-06-11 | 1997-06-11 | |
| US08/872,726 | 1997-06-11 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2240119A1 true CA2240119A1 (en) | 1998-12-11 |
Family
ID=25360189
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2240119 Abandoned CA2240119A1 (en) | 1997-06-11 | 1998-06-08 | Over-temperature sensor cable and electrical cord with over-temperature protection |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2240119A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9787083B2 (en) | 2012-12-06 | 2017-10-10 | Twin-Star International, Inc. | Overheat-resistant power cord and method |
-
1998
- 1998-06-08 CA CA 2240119 patent/CA2240119A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9787083B2 (en) | 2012-12-06 | 2017-10-10 | Twin-Star International, Inc. | Overheat-resistant power cord and method |
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