Abstract: Apparatus for automatically disconnecting a conductive polymer heater if an arcing fault occurs. A sensor conductor is incorporated into the heater, so that if an arcing fault occurs, the current through the sensor conductor increases and triggers a safety circuit to disconnect the heater. The sensor conductor is preferably insulated by an organic polymer which pyrolyses if an arcing fault occurs and thus permits current to flow between the sensor conductor and an electrode of the heater.

Abstract: A liquid or gel filled pillow utilized for therapeutic purposes is formed from a pair of flexible casing of plastic or the like, one within the other, and being separated by a compressible electrically conductive foam material having a high resistance in its uncompressed slate and a low resistance when compressed. The facing surfaces of the casings are coated with a layer of highly conductive material in electrical contact with the foam. The inner casing is provided with a thermostatically controlled heating element for heating the liquid or gel contained therein. One terminal of the heating element is connected to the power supply through the conductive layers foam so that upon compression of the foam, as would be occasioned by a patient laying his head upon the pillow, there will result an electric current flow to the heating element due to the lowered electrical resistance of the foam.

Abstract: A heat tracing tape which can be cut to required lengths has a heating element comprising at least two lengths of woven or braided resistance wire each in the form of a flat strip. The strips are encased in extruded silicone rubber whereby they are spaced from one another. The strips are electrically connected at one end by a connector and the tape is provided with a power supply termination either at its other end, or at a T-branch connection, for connecting the tape to the power control system. The power control system is adjustable to set an estimated value of power required to maintain a predetermined process temperature. The system automatically adjusts the power supplied to the tape to the estimated value by means of a feedback control system. A process temperature sensor also regulates the power supplied to the tape in accordance with a sensed temperature.

Abstract: Method for monitoring the electrical integrity of a heater and a novel heater for use in such a method. The heater includes an elongate heating member; an insulating jacket which encloses the heating member; a first electrically conductive member which surrounds the insulating jacket; a separating and insulating member which surrounds the first conductive member; and a second electrically conductive member which surrounds the first conductive member and is separated and insulated therefrom by the separating member. The method includes the step of testing the electrical relationship between the first and second electrically conductive members.

Abstract: A portable electric hair dryer includes an electric heater and blower forming a load circuit energized from a pair of power feeder lines connected to a source of AC power. A zero phase-sequence current transformer is electrically coupled to the power feed lines between the connection thereof to the power source and the load circuit to serve as a current leakage detector. An electricaly conductive heater enclosure disposed within the housing of the hair dryer receives the heater and is electrically isolated from the power feed line serving as the hot line. The heater enclosure is electrically connected to the power feeder line serving as the neutral line by a ground wire extending between the heater enclosure and the point at which the zero phase-sequencing transformer is coupled to the power feeder lines to define a leakage current path between the hot line and the heater enclosure should the hair dryer be dropped in water.

Abstract: Electrical energy being supplied to an electrical heater, typically a glow plug within an internal combustion engine (ICE), is easily and simply controlled by controlling the duty cycle or ON/OFF duration of a switch (10) serially connected between the glow plug (11) and a supply voltage source, for example a vehicular battery (U.sub.Batt). An operational amplifier (15) controls the duty cycle of the switch (10) by comparing a periodically varying voltage (37a) derived from a stabilized frequency or pulse generator (30) with battery voltage (U.sub.Batt) and, at the cross-over points, respectively changing the switching condition of the switch. Upon drop in battery voltage, the switch will be longer in an ON position than at a higher battery voltage, so that the average voltage, over a plurality of cycles, across the glow plug (11), will have a value (U.sub.KEM) which will result in a predetermined temperature thereof.

Abstract: A smoke detector is mounted externally of but adjacent to an electric kitchen range and supplies an electrical signal when smoke is detected. Such signal actuates a relay to interrupt the supply of power to the range. The relay can be interposed between the range plug and its wall receptacle so that no modification to the internal range circuitry is required, and can require a manual resetting operation before the supply of power to the range is resumed.

Abstract: The bushing balance controller is an electronic device which measures the voltage drop across each segment of a multiple segment glass fiber forming bushing and measures the current flow in the bushing. The device uses these measurements to produce error signals proportional to the difference in the set point temperature and the instantaneous temperature of each segment of the bushing. The device diverts current from each segment of the bushing whose error signal is greater than the average of the error signals for all segments of the bushing. The device also sums all error signals and passes this signal to a bushing controller which adds current to the bushing when the sum of the error signals falls below a preset value.

Abstract: An electrical heating apparatus protected against an overheating condition and a temperature sensitive electrical sensor for the use therewith are disclosed. The electrical heating apparatus includes an electrical heater for generating heat in proportion to the amount of electricity flowing through it, and it provides essentially all the heat for the apparatus. An electrical sensor is disposed in a thermally responsive relationship to the electrical heater. The electrical sensor includes a coextruded pair of spaced flexible plastic conductors and a coextruded flexible temperature sensitive electrical impedance material having predetermined temperature coefficient impedance characteristics along its entire length. The temperature sensitive material is in electrical contact with the flexible conductors and controls the flow of electricity between them.

Abstract: A timer for controlling the roasting of food products which create sounds during the roasting process through the explosive release of steam and gases generated by the cooking process. The system includes a transducer to sense sound and generate a control signal upon the cessation thereof.

Abstract: A circuit and method for interrupting power applied to an electrically conductive panel such as a vehicle windshield or window upon cracking of the conductive coating or element thereon. The circuit includes structure for (1) monitoring the resistance of the conductive element and (2) interrupting power applied thereto when the resistance of the conductive element assumes a value indicative of element cracking.

Abstract: A safety switch for a glass door, which is used for refrigerating and deep freeze chambers and comprises two or more glass panes of hardened glass, of which the front pane (21) remote from the refrigerating and deep freeze chamber is heated by an electrically conductive layer attached on the inner surface of the pane, which layer is connected to an upper and, respectively, lower collecting conductor, and the rear pane (22) facing to the refrigerating and deep freeze chamber is provided with at least one conductor attached on the pane. The conductors are connected to a current scanning device (20), which is capable to scan whether current flows through said collecting conductors and the conductor of the rear pane, and which is capable to break the connection between the conductors of the two panes (21,22) and a voltage source (46) in the event that current does not flow in the collecting conductors and/or in the conductor of the rear pane.

Abstract: In combination with an electrical appliance, an automatic warning circuit to warn a user of an electrical hazard wherein the warning circuit comprises a timing circuit responsive to turn-off of the electrical appliance for generating a triggering signal after lapse of a predetermined time period after turn-off thereby to energize an audible alarm. The timing circuit and alarm are useful for warning a user of the appliance of an electrical safety hazard brought out by the appliance being connected to a power line while not being used.

Abstract: The controller of the present invention regulates the flow of current through a resistive heating element by computing the predicted resistance R.sub.hot of the heating element at the desired temperature and then adjusting the voltage drop across and current flow through the resistive heating element until the relationship V=IR.sub.hot is satisfied. In an analog embodiment of the present invention, measurement of the voltage drop is obtained from a voltage amplifying circuit connected across the resistive heating element, while a measure of the current flow through the resistive heating element is obtained from a current amplifying circuit connected across a current measuring resistor in series with the resistive heating element. The output of the current amplifying circuit is multiplied by first and second variable gain amplifier circuits to produce a signal output representing the product of the current flow and the predicted resistance at the desired temperature.

Abstract: The automatic temperature control device for an electric appliance such as an electric blanket comprises a heater element, a sensor made of a thermosensitive material having an impedance, which changes as the temperature varies, for detecting the temperature of the heater element, switching means for regulating the supply of electric power to the heater element, and a plurality of electric circuits for driving the switching means in response to the output signal from the sensor. The plurality of electric circuits function to prevent the sensor from being polarized and to detect a temperature signal by applying thereto an alternating current, to detect a failure occurring in the electric circuits in synchronism with zero-crossing pulses, and to detect a failure occurring in the switching means, thereby assuring a safe operation of the automatic temperature control device against the occurrence of any failure.

Abstract: A protective circuit arrangement for sheathed heating elements which interrupts ground fault conditions by effectively decoupling the power line from the heating element regardless of the polarity of the power supply connections. A fusible link couples each side of the heating element to the power supply. A normally open switch responsive to current in the ground path switches a relatively low resistance shunt current path across the heating element when the ground current exceeds a predetermined threshold level. Closure of the shunt path enables sufficient current to flow in the power supply lines to actuate the fusible links. Circuit parameters are selected such that the current in the fusible link coupled to the hot power line is sufficiently greater than that in the fusible link coupled to the neutral line to cause the hot power line fusible link to be actuated first, thereby interrupting the fault condition and decoupling the hot power line from the heating element.

Abstract: A control for a thermal oven having a manually settable timer for establishing preselected broiling and baking times. The control includes an alarm and circuitry for sounding the alarm at the end of the timed cooking period. The control further de-energizes the heating elements a short preselected time after the time period set by the user in the event the user does not take affirmative steps in response to the alarm. The control continues to provide a reminder alarm operation at predetermined intervals, such as five-minute intervals, until such time as the user provides the affirmative input to terminate the control operation and reset the system.

Abstract: An electrical resistance heater controller is provided with a plurality of circuit branches connected in parallel with each other and in series with a heating element and an external AC power source. Each circuit branch includes the series connection of a capacitor and a solid state switch. The switches are controlled by a gating device to switch during the zero crossing of the AC source voltage waveform. Power delivered to the heating element is controlled by varying the amount of series capacitance in the circuit.

Abstract: In an engine preheating control system, in which the temperature of glow plugs mounted in a diesel engine is held in a constant high temperature range during the cranking operation after the closure of an engine key switch through the control of power supply to the glow plugs based upon the detection of changes of the resistance of the glow plugs, a main relay for controlling the power supply from a power supply source through a current detecting resistor to the glow plugs and a sub-relay for controlling power supply through a stable preheating resistor and the detecting resistor to the glow plugs are energized and de-energized in response to first to fourth control signals.

Abstract: A power disconnect assembly for a plug-in electric heating element adapted to support and heat a cooking vessel and its contents. The assembly includes a terminal block with terminals for receiving the plug-in heating element and supplying electrical power thereto. A double pole switch with contacts connected to line voltage and to the terminal block is provided and a solenoid is utilized to open and close the double pole switch. Means are provided to detect the presence and absence of a cooking vessel on the heating element and means cooperating with the cooking vessel detection means to deenergize the solenoid in the event of cooking vessel absence and open the double pole switch thus terminating electrical power to the terminal block.

Abstract: A heating arrangement in a fixing station of a printing device has its operation monitored by an arrangement in which a measuring element is disposed in series with the heating element and a switch element. The measuring element is traversed by the heating current and emits a corresponding voltage which is supplied to an amplifier circuit which produces pulse-shaped clock signals as long as the heating current flows through the measuring element and the heating element. The clock signals are supplied to a reset input of a flip-flop whose dynamic input is connected to an oscillator operating at a frequency lower than that of the alternating current so that as long as clock pulses occur, the flip-flop is constantly reset. Therefore, the flip-flop can only be set over a longer interval when no heating current is flowing.

Abstract: An electric blanket control effective to deactivate power to the blanket's resistance wire heating circuit, the control having a capacitance detector constructed and adapted to respond to differences in the capacitance of the heating circuit attributable to the presence or absence of the user under the heating wire of the blanket, and a switch responsive to the detector adapted to interrupt power to the heating circuit when the capacitance value of the heating circuit indicates the absence of the user.

Abstract: In an improved control circuit for the heating current of a system for developing latent photographic images on a heat developable medium, an incipient loss of tension in the record medium is sensed by detecting high frequency components of the energizing current incident to incipient arcing at the heating electrodes. The resulting signal is utilized to interrupt the flow of current to the heating electrodes, to prevent further arcing and the danger of fire. A time delay feature is incorporated to restore the heating current after a predetermined delay. If the tension in the record medium has not been restored, then the incipient arcing will again cause an interruption of the heating current.

Abstract: A power control arrangement for controlling the power output of a resistive heating element of the type having a fast thermal response time and a highly variable resistance with temperature. The power control arrangement includes a plurality of operator selectable power settings and an electronic switching system responsive to operator selection of these settings to rapidly couple and decouple a power supply to the element. The switching action is selected to permit rapid heat up of the element without causing an unacceptable current to flow and to prevent excessive cooling of the element after it reaches operating temperatures during steady state operation.

Abstract: Frying apparatus including a fry pot and a filter system operable during a cleaning cycle for dislodging food particles which cling to the fry pot and for removing food particles suspended in the cooking oil is disclosed. The filter system includes a shower apparatus which discharges jets of cooking oil along the interior side surfaces of the fry pot to dislodge food particles clinging thereto. The cooking oil is drained into a drain pan, strained through a filter and means are provided for pumping the filtered cooking oil back to the fry pot where it is discharged through the shower apparatus. Food particles are continuously separated from the cooking oil as it is conveyed from the fry pot through the filter into the drain pot. In a preferred embodiment, a control circuit is provided for automatically turning off the fry pot heaters when the cooking oil is drained during the filter cycle.

Abstract: In a system in which temperature control of a heated region is critical, assurance means of fail-safe nature are provided to guard against improper temperature. An example wherein temperature is critical is: the artificial ventilation of an unconcious patient's lungs by periodically inspired heated gas under pressure. The assurance means includes dual thermometers which sense the actual temperature in the heated region. The actual temperature is compared with the desired temperature to control an electric heater, which, when energized, increase the temperature of the heated region. Furthermore, the temperatures, as sensed by the two thermometers, are compared with each other. If the difference exceeds a predetermined limit, an alarm is given and the heating system is shut down.

Abstract: A primary thermostat is provided in a fryer of the type comprising a frypot containing cooking oil, a heater, heat control switching means for operating the heater and a thermostat including a temperature probe, the fryer thermostat being used as a backup to the primary thermostat. The primary thermostat utilizes the signal of a temperature probe associated with a cooking computer which calculates the cooking time period for food items cooked in the fryer. The primary thermostat includes comparators monitoring for open or shorted conditions of the cooking computer temperature probe, and a control transfer relay which switches thermostatic control of the fryer from the primary to the backup fryer thermostat in the event of probe failure. The primary thermostat also includes a temperature selection switch for selecting a desired temperature of the cooking oil and temperature control circuitry for operating the fryer heater to maintain the desired temperature.

Abstract: An electrical heating apparatus, and particularly a bedcover preferably in the form of a blanket, protected against an overheating condition and in which electrical current flow through a heating element is controlled by a pair of gate controlled bidirectional semiconductor switches electrically connected to one another in series and in front-to-front orientation. The gates of the semiconductor switches are connected through a temperature sensitive capacitor which triggers the semiconductor switches from a conductive to a nonconductive state in response to the sensing of an overheating condition.

Abstract: A structure adapted for use in a door of a refrigerated compartment. The door may include a plurality of panes of glass, a plurality of spacers for spacing the plurality of panes of glass so as to form an air space between each pair of panes of glass, a conductive coating applied to one surface of one of the panes of glass facing into the air space between the panes of glass, and an electrical circuit connected to the conductive coating on the coated surface of the pane of glass. The electrical circuit includes a portion which could otherwise be exposed to physical contact through the air space in the event of breakage of the coated or opposing pane of glass. The structure includes a portion for blocking physical contact with the portion of the electrical circuit which could otherwise be exposed. The structure further includes portions for connecting with the spacers in the door for securing the structure in the door.

Abstract: A clamp heater for heating shoe upper portions prior to molding them comprises an inner metal form and a cooperating outer band constructed of silicone rubber. The inner metal form has a cartridge heater accommodated therein. The outer band is heated by a radiant heater arranged about its outer surface. When the inner form carries a shoe upper portion into the outer band, the outer band wraps around the shoe upper portion and clamps it about the inner form, to ensure efficient heat transfer. To protect the outer band from heat damage, a temperature control device in the form of a thermostat is provided. The inner form also has a temperature control device therein. To ensure adequate heat is available in the operation of the clamp, when the inner form is moved to carry the shoe upper portion into the outer band, the temperature controls are both overridden and the heaters are rendered operative.

Abstract: A control circuit for proportionally controlling the application of available ac current to thin film heaters and other heating apparatus for transparent windows and other selected surfaces of refrigerated cabinets prevents condensation of moisture thereon. A transducing sensor in contact with the ambient air and thermally coupled to the refrigerated cabinet surfaces provides control signals to an ac heating current control circuit in relation to the difference between cabinet surface temperature and the dew point temperature of the ambient air. As the cabinet surface temperature drops closer to dew point the application of electric power to the transparent window and other surface heating apparatus is proportionally increased by the control circuit by applying heater current during correspondingly increased "on" periods for passage of the available ac heater current. "On" periods of the heater current are initiated during times in a cycle when the ac is at or near its null.

Abstract: In one embodiment, a sheathed electrical resistance heating unit is operated from a 120 volt unbalanced-to-ground household power line. The heating unit sheath is grounded. In order to interrupt a fault between the actual resistance heating element and the outer sheath of the heating unit, regardless of where along the length of the heating unit the fault occurs, a fuse is connected in series with the "hot" side of the power line, and, by means of at least one unidirectional current conducting device, the two terminals of the heating element are effectively connected, through the fuse, to the "hot" side of the power line during alternate AC half-cycles.

Abstract: Circuit for controlling the program timer of a laundry dryer as a function of the moisture-dependent resistance of the laundry. A storage capacitor charged from a d-c voltage source together with laundry resistance resulting from wet laundry bridging two electrodes and resistance determine the duty cycle or frequency for an oscillator. The output of the oscillator is fed to a filter and from there as one input to a comparator. A reference value setter is fed to another input of the comparator. The output of the comparator is functionally connected to the program timer. This circuit arrangement makes possible measurement of low residual moisture values in the laundry and thereby permits the start of the post-drying phase without heating on reaching this low residual moisture value.

Abstract: A control instrument is provided for electric cooker plates. The instrument comprises an adjustable quantizing power control instrument having an expansion element with an electric heating element and a time switch member for increasing the power adjusted on the power control instrument for a period in the initial cooking phase. The time switch member comprises an electronic counter timing member and at least one divider which, via an electronic switch element, reduces the power supplied to the heating element in a predetermined division ratio.

Abstract: A low voltage protection circuit for an air conditioner compressor which employs a series of diodes to control the application of an a.c. source potential to the resistive heater element of a conventional thermally responsive switch. The diode circuit maintains the heater element directly across the source potential at all times when the thermally responsive switch is open, but only during alternate half-cycles of the source potential when the thermally responsive switch is closed to thereby protect the compressor against potentially damaging low voltage conditions while reducing the power consumed by the heater element during periods of normal source voltage level.

Abstract: An electric resistance humidifier which increases atmospheric humidity by boiling water in a tank. Spaced conductive plates, or electrodes, are fixed in the tank. As the tank water level rises, the immersed area of the electrodes increases. An electric supply causes the electrodes to pass electric current through the tank water therebetween for heating and vaporizing such water. Electric current and heating cease automatically when the tank water level falls below the electrodes. A control includes comparator circuitry responsive to a reference signal and a signal related to electrode current for actuating and deactuating a water supply to the tank. In one embodiment, the control includes further comparator circuitry responsive to electrode current and a further reference signal for controlling a tank drain, to compensate for rising conductivity of the tank water as it warms toward boil and thus prevent substantial overshoot in heating current flow.

Abstract: An appliance or device for treating hair includes a tubular barrel containing a generator for heat and vapor and a plurality of hair winding mandrels which are slidably mounted over the tubular barrel. The mandrels have different external sizes and configurations, but have interior structures which, though they may differ, allow each mandrel to be used with the same tubular barrel.

Abstract: A window has a heating grid and a moisture sensor formed thereon for connection to a detector which automatically controls the heating. The sensor has an output terminal and another terminal connected to a heating conductor, the sensor being positioned outwardly of the heating grid with the area of the sensor including the output terminal lying in the heating zone. Advantageously the outer limit of the sensor is closely adjacent the outer limit of the heating zone. The output terminal is positioned between the outward limit of the sensor electrodes and the boundary heating conductor. A shield electrode connected to the heating conductor may be provided. The sensor may be located between a pair of heating conductors adjacent a heating grid collector with one electrode connected to the conductors. For deep windows, the sensor may be located in an offset branched section of a boundary heating conductor.

Abstract: The invention relates to a safety control shut-off device for the heating element of a cooking stove. In one embodiment of this safety device, a burner plate of the stove is provided with several declining U-shaped grooves for collecting any spillage or overflow of water from the cooking operations. Water drops collected in the declining grooves are led through a discharge outlet, at the lowest portion of the grooves, and into a water drop detector located beneath the outlet, to complete an electrical circuit, which in turn will actuate and sound an alarm and will also actuate means for disconnecting the fuel source of the plate burner.

Abstract: Apparatus for controllably heating a vehicle window having a heating grid is described including an oscillator and a signal detector, with a signal circuit coupling the oscillator and the signal detector having a DC voltage component at one or more points thereof. One or more humidity detectors are coupled to the signal circuit to control the amplitude of the oscillations supplied from the oscillator to the signal detector, advantageously by voltage divider action, and capacitor means provides DC isolation between the humidity detector(s) and any DC voltage component in the signal circuit, and also between humidity detectors when a plurality are used. Advantageously the humidity detector(s) are directly connected to the heating grid, and varying DC voltage levels at the point(s) of connection to the grid are isolated by the capacitor means. Particular arrangements of the humidity detectors on the window and connections to the heating grid are described.

Abstract: A heating panel safety system has electrodes on opposite sides of the heating panel which supply conductive material. A first lead wire has ends connected to spaced terminals on a first electrode, and a second lead wire has ends connected to spaced terminals on a second lead wire. Turns in the lead wires are coupled via a core with a turn in a relay energizing wire. Normally closed circuit breaker contacts of the relay are opened when the relay is energized by a bias current in one of the lead wires, such as caused by a discontinuity in an electrode. Opening of the circuit breakers stops flow of current from a power source to the lead wires.

Abstract: An electrically heated window for a vehicle includes a smooth surfaced transparent sheet having a plurality of spaced electric resistance heating conductors on the surface thereof. A humidity detector is provided on the inside surface of the sheet and includes two sets of conductors standing in relief above the surface of the sheet and each having substantially the shape of a comb with the teeth of the two combs interdigitated and extending substantially in the direction of maximum slope of the sheet. The back of the upper comb defines a gutter for the diversion of water droplets from the area occupied by the teeth of the combs.

Abstract: A frangible panel having an electrically-energizable layer carried in an area thereof for heating the panel and main circuit means for supplying electrical power to the layer is provided with circuit breaker means operable to interrupt electrical power to the layer upon breakage of the panel. The circuit breaker means includes a fusible link connected in series with the layer and a solid-state control device connected in the main circuit in parallel with the layer. The solid-state device has a control gate which is connected to a sensing circuit surrounding the electrically-energizable layer and which is connected in the main circuit to render the solid-state control device non-conductive as long as the sensing strip is continuous and to render the solid-state control device conductive when the sensing circuit is broken. Thus, the solid-state control device connects the fusible link to ground and causes the link to blow, thereby interrupting power to the electrically-energized layer.