Portable electrical appliance with object sensing assembly

A portable electric appliance includes a housing, an electrically operable element positioned within the housing, a transmitter adapted to transmit a beam of radiation, and a receiver responsive to the beam of radiation. The transmitter is positioned external to the housing, and the receiver is positioned to receive the beam of radiation. The electrically operable element is de-energized in response to the beam of radiation being blocked or interrupted. A method adapted to disable a portable electric appliance includes transmitting a beam of radiation from a transmitter on the portable electric appliance, receiving the beam of radiation by a receiver on the portable electric appliance, and de-energizing an electrically operable element associated with the portable electric appliance in response to the beam of radiation being blocked or interrupted.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to portable electrical appliances such as heaters having sensors for detecting objects that may interfere with their operation.

2. Description of the Related Art

Portable appliances, such as heaters, have been provided with various sensors for determining whether an object is too close to them. Such sensors may be in the form of mechanical detectors as disclosed in U.S. Pat. No. 4,906,818. Electronic sensors have also been used to shut off a heater in the event an object is too close to the heater outlet. U.S. Pat. No. 5,805,767 discloses the use of motion sensors for this purpose. U.S. Pat. No. 6,091,888 discloses the use of infrared or ultrasonic proximity detectors for detecting a stationary or moving object within a predetermined distance of the heater inlet or outlet.

SUMMARY OF THE INVENTION

A portable electric appliance is provided that includes a housing having electrically operable elements and an outlet. A transmitter is mounted to the housing near the outlet and is capable of transmitting a beam of radiation. A receiver is mounted to the housing in opposing relation to the transmitter. The receiver is positioned to receive the beam of radiation from the transmitter. A control circuit is provided for deactuating the appliance in response to interruption of the beam between the transmitter and the receiver.

In one embodiment of the invention, the transmitter is an infrared transmitter and the receiver is an infrared receiver, both of which are positioned above the outlet as shown inFIG. 1. The appliance preferably includes an encoder for encoding the beam from the transmitter. A decoder is preferably provided for determining whether a correct signal has been received by the receiver from the transmitter. If a correct signal has not been received within a preselected period of time, the appliance and/or electrically operable elements are disabled and/or de-energized.

A transmitter, receiver, and control circuit as described above can be employed in association with various electrical appliances. For example, a portable humidifier can be equipped with a radiation transmitter and a detector near an inlet and/or outlet. A control circuit will shut down the humidifier if an object covers the inlet or outlet, thereby interrupting the beam from the transmitter to the detector. The appliance can alternatively be an electric heater.

A cover detector circuit is provided by the invention that checks for the presence of the infrared signal or other radiation signal sent by the transmitter. If a fault is detected, a control circuit, such as a microprocessor, microcontroller, or application specific integrated circuit (ASIC), stops the operation of the appliance. In the case of automatic heaters, the ASIC disables triac pulses. In the case of manual heaters, the 110 VAC supply is interrupted. The ASIC further may cause an LED or other indicator to be actuated when the path between the transmitter and detector is blocked. In a preferred embodiment, the ASIC must not receive a correct signal for a selected period of time (e.g. approximately 2.8 seconds) before it will disable the appliance. Short interruptions are ignored. Once a fault is detected and the appliance is disabled, the transmit signal needs to be detected correctly for a predetermined period before the ASIC will reset itself, turn off the LED and re-enable the appliance.

A portable electric appliance is provided in accordance with a preferred embodiment of the invention, which includes a housing, an electrically operable element positioned within the housing, a transmitter adapted to transmit a beam of radiation, and a receiver responsive to the beam of radiation. The transmitter is positioned external to the housing, and the receiver is positioned to receive the beam of radiation. The electrically operable element is de-energized in response to the beam of radiation being blocked or interrupted.

The transmitter may include an infrared or laser transmitter, and the receiver may include an infrared or laser receiver. The portable electrical appliance may include a heater, and the electrically operable element may include a heating element. The beam of radiation may be transmitted as pulses, and the electrically operable element may be de-energized in response to the beam of radiation being at least one of blocked or interrupted for a predetermined period of time.

The beam of radiation may be transmitted having a first value of an electrical characteristic, the beam of radiation may be received having a second value of the electrical characteristic, and the electrically operable element may be de-energized in response to the second value being unequal to the first value for a predetermined period of time. The electrical characteristic may include at least one of duty cycle, on-time, off-time, intensity, amplitude, and frequency.

The electrically operable element may be energized in response to the beam of radiation being unblocked or uninterrupted for a predetermined period of time. The beam of radiation may be transmitted having a first value of an electrical characteristic, the beam of radiation may be received having a second value of the electrical characteristic, and the electrically operable element may be energized in response to the second value being equal to the first value for a predetermined period of time.

A method adapted to disable a portable electric appliance is provided in accordance with a preferred embodiment of the invention, which includes transmitting a beam of radiation from a transmitter on the portable electric appliance, receiving the beam of radiation by a receiver on the portable electric appliance, and de-energizing an electrically operable element associated with the portable electric appliance in response to the beam of radiation being blocked or interrupted.

These and other objects, features, and advantages of this invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A portable appliance in the form of a heater10is provided with an object sensing assembly that causes power to be interrupted or shut off if an object near the heater outlet is sensed. Referring toFIG. 1, the heater10includes a housing12having a front wall14that includes an outlet16. A grill18having vanes is provided in the outlet16. The vanes can be fixed or movable. Other types of heater grills are well known. Some, for example, include metal panels having rows of circular openings to allow the passage of heated air.

The top wall of the heater includes a control panel20. The control panel may include a power button21for turning the heater on and off, a timer button (not shown) for setting the time of operation, and controls for adjusting a thermostat and/or controlling the amount of heat to be generated. These and other controls are known to the art.

The heater10shown inFIG. 1includes one or more heating elements (not shown) that can be selectively operated. A fan (not shown) is present within the housing for moving air over the heating elements and through the outlet16. Air can be drawn into the housing through one or more air inlets (not shown) in the rear wall of the housing or other suitable location. The heating elements can be resistance heating elements. Other types of portable heaters are known to the art, including radiant heaters that do not require the use of a fan. Such heaters may lack a grill.

The heater10includes an object sensing assembly that includes at least one radiation transmitter assembly22and at least one radiation receiver assembly24for receiving signals from the transmitter. As shown onFIG. 1, both the transmitter and receiver are mounted above the outlet16. If the radiation path between the transmitter and receiver is interrupted, the heater is shut off. As discussed below, the radiation path must preferably be interrupted for a preselected time duration before the heater shuts off. While the heater could be shut off following a momentary interruption, such an arrangement is not preferred.

The locations of the transmitter22and receiver24assemblies are shown as being above the outlet. Obstructions, such as drapes or clothing items that may extend over the heater, will be readily detected. The transmitter and receiver assemblies preferably extend only a short distance from the front wall and are unobtrusive. Each is positioned near a side wall of the heater. The distance between the transmitter and receiver assemblies preferably at least generally corresponds to the maximum width of the outlet.

FIG. 2is a schematic diagram of a first embodiment of a circuit26to perform the object sensing function in accordance with the present invention. The object sensing circuit26preferably includes a cover detector application specific integrated circuit (ASIC)28, which is connected at pin1to a 5 VDC power source provided by operation of Zener diode30and capacitor32. Capacitor32and Zener diode30are connected in parallel across ground and a 110 VAC power supply, which is coupled to connector34. Specifically, the anode of zener diode30is connected to ground and the cathode of zener diode30is coupled to connector34. The 5 VDC power source is thus available at the cathode of zener diode30.

The frequency of a clock signal internal to the cover detector ASIC28is controlled by resistor36and capacitor38. Specifically, resistor36is preferably connected in series between pins1and2of a cover detector ASIC28. Capacitor38is preferably connected in series between pin2of the cover detector ASIC28and ground.

The neutral or ground connection associated with the 110 VAC power source is preferably coupled to connector40and provided through resistor42to pin3of the cover detector ASIC28. Capacitor44is connected in series between the cover detector ASIC28and ground, thus providing a direct connection to the 110 VAC line voltage and the cover detector ASIC28at pin3to enable it to operate whenever the heater is plugged in.

The output of an infrared (IR) receiver46, incorporated as part of the receiver assembly24shown inFIG. 1, is preferably connected to pin4of the cover detector ASIC28. The receiver46is connected to the 5 VDC power source (VCC) through a filter, which includes resistor48and capacitor50. Specifically, capacitor50is connected in series between the IR receiver46and ground, and resistor48is connected in series between the IR receiver46and the 5 VDC power source. The IR receiver46is also connected to ground.

A switch52is preferably connected in series between pin12of the cover detector ASIC28and ground, and a switch54is preferably connected in series between pin5of the cover detector ASIC28and ground. Switch52is preferably used to manually turn the heater on and off, and switch54is preferably used to enable or disable a timer mode. The power button21on the heater controls the on/off status by means of the switch52. The power is off by default (at power-on), and each push of the button will change the on/off status. While a power LED is not provided in the embodiment ofFIG. 2, such an LED or other indicator could be used to indicate whether power is on or off.

The timer mode enables the heater to remain on for a predetermined period of time and to thereafter automatically turn off. In a preferred embodiment, the timer turns the heater off after about four hours. The power needs to be on before the timer can be used. The timer LED is turned on when the timer is activated. It provides steady illumination during the four-hour period, then flashes at a given rate (e.g. 400 ms on, 400 ms off, etc.) to indicate that the heater is off because the time has expired. If the timer button (not shown) is pushed while the timer is active, the timer function will be cancelled and the timer LED will turn off. If the heater is off because time has expired, only the power button (not shown) can be used to turn the heater back on.

The cathode of diode58is preferably connected to the neutral or return of the 110 VAC supply at connector40and half-wave rectifies the AC supply. Resistors60and62are preferably connected in series between the anode of diode58and ground to limit the current through diode58. Current flows from the hot side of the AC line at connector34through Zener diode58, resistor62, resistor60, and back to the neutral side of the AC line at connector34producing voltage across Zener diode58. Since Zener diode30is connected from VCC to ground, a regulated voltage is created.

Light emitting diode64preferably provides an indication of when the heater is covered and diode66indicates when the heater is in the timer mode. The anode of diode64is preferably connected to the 5 VDC supply and its cathode is connected to pin11of the cover detector ASIC28. Resistor68is connected in series between pin11of the cover detector28and the cathode of diode64. Similarly, the anode of diode66is preferably connected to the 5 VDC supply and its cathode is connected to pin10of the cover detector ASIC28.

Resistor70is preferably connected in series between pin10of the cover detector ASIC28and the cathode of diode66. Thus, in response to pin11of the cover detector ASIC28being substantially grounded, diode64is illuminated, and in response to pin11being at or near 5 VDC, the diode64is turned off. Diode66operates in a similar manner in response to control by voltage levels output on pin10of the cover detector ASIC28.

The cathode of infrared (IR) LED or transmitter72is preferably connected to ground and a resistor74is connected in series between pin6of the cover detector ASIC28and the anode of IR LED72. The IR LED72is incorporated in the transmitter assembly22shown inFIG. 1and provides the infrared signal to be received by the IR receiver46, as described above.

Pin8of the cover detector ASIC28is preferably connected through resistor75to pin1of an optoisolated triac driver MOC3010, which is commercially available from Fairchild Semiconductor Corporation (www.fairchildsemi.com). Further details concerning the triac driver MOC301084are provided in the “Random-Phase Optoisolators Triac Driver Datasheet”, pp. 1-10 (2005), which is incorporated herein by reference. Capacitor76is connected in series between pin8of the cover detector ASIC28and ground, and operates to filter spikes that may occur on the AC supply to the heater.

A triac78selectively switches the 110 VAC supply coupled to connector80to the heater, which is coupled to connector82. Pin4of a triac driver MOC301084is preferably connected to a gate of the triac78and operates to control switching of the 110 VAC supply to the heater. Resistor85is preferably connected in series between connector82and pin6of the triac driver MOC 301084to limit the gate current provided to the triac78.

FIG. 3is a schematic diagram of a second embodiment of an object sensing circuit29to perform the object sensing function in accordance with the present invention. The second embodiment is essentially the same as the first embodiment described in connection withFIG. 2, except that the on/off switch and timer mode have not been implemented in the second embodiment, and thus switches52,54, diode66, and the circuitry associated therewith have been omitted. In addition, indication of the cover detector function is provided through pin7of the cover detector ASIC28, which is connected to pin6of a safety check ASIC86for this purpose.

The safety check ASIC86preferably indicates whether the object sensing assembly and/or other features of the heater are indeed operational when the heater is turned on. It may cause various indicators, such as LEDs associated with pins7-10thereof to illuminate if certain elements are inoperable.

In addition to the cover detector ASIC28, other elements that can be tested for operability include a PTC breaker, a thermal fuse, and a tilt switch. As such an ASIC is not a necessary part of the invention described herein, further discussion of the ASIC is not provided. Additional LEDs88-94are provided for indicating when the tilt switch, thermal fuse, PTC breaker, and cover detector ASIC, respectively, have detected an abnormal condition.

A further distinction between the embodiments is that the cover detector ASIC28inFIG. 3preferably controls whether the heater is turned off or not through action of the output at pin9of the cover detector ASIC28rather than pin8of the cover detector ASIC28shown inFIG. 1. Thus, the circuitry, which includes the triac78, optoiosolated triac driver MOC301084, resistor75, and capacitor76shown inFIG. 2have been omitted inFIG. 3. The cover detector ASIC28shown inFIG. 3preferably controls whether or not the heater is turned off by means located in a position remote to the circuit shown inFIG. 3.

FIG. 4is a schematic diagram of a third embodiment of a circuit50to perform the object sensing function. The circuit50is substantially similar to that shown inFIG. 3, except that the IR diode72has been replaced with a laser diode or transmitter86and the IR receiver46has been replaced with a photo-sensitive transistor88. In addition, the value of resistor98has been modified and capacitor50has been eliminated to accommodate different electrical characteristics of the photo-sensitive transistor88.

FIG. 5is a schematic diagram of the heater, which may incorporate any of the object sensing circuits described above. The heater includes a heater assembly100including a pair of resistance heating elements102,104. The heating elements can be selectively operated to vary the heat output of the heater. Triacs106and108are connected in series between the respective heating elements102,104, and signals provided at terminals TRIAC1110and TRIAC2112of a printed circuit board (PCB) control the TRIACS106,108, respectively. A fan motor114is provided for causing a fan to blow air by the heating elements, thereby heating the air prior to its exiting the outlet16shown inFIG. 1.

The fan is selectively energized by a signal from the PCB at connector116. An oscillating motor118is provided for oscillating the fan, thereby directing heated air in various directions as the fan oscillates back and forth. The oscillating motor is selectively energized by a signal from the PCB at connector120. The heater can be operated with or without fan oscillation. The heater can also function as a fan when neither heating element is operated. The oscillating motor can alternatively cause the heater housing to oscillate back and forth about a vertical axis.

The heater includes various safety features in addition to the sensing assembly described above and shown inFIG. 2,3, or4. A tilt switch132shown inFIG. 3is provided for cutting power to the heater assembly100and fans114and118if the heater is tilted beyond a predetermined amount. The tilt switch is connected to connector124of the printed circuit board. A thermal fuse126and a positive temperature coefficient breaker128are connected in series between the source of AC current and the PCB at connector130. They are also connected to the triacs106and108. Power to the heater assembly100is disconnected in the event of an overheating and/or over-current condition by operation if the fuse126and/or breaker128.

FIG. 6shows a second embodiment132of the heater formed in accordance with the present invention, which is substantially similar to that shown inFIG. 1, except that there are preferably three sets of radiation transmitter and receiver assemblies22,24. The assemblies22,24are preferably located along the left and right sides of the grill18. In addition, air inlets19, a power button134, and a power indicator136are provided along the lower front side of the heater132. The heater10shown inFIG. 1includes one or more heating elements (not shown) that can be selectively operated. A fan (not shown) is present within the housing for moving air over the heating elements and through the outlet16. Air can be drawn into the housing through one or more air inlets (not shown) in the rear wall of the housing or other suitable location. The heating elements can be resistance heating elements. Other types of portable heaters are known to the art, including radiant heaters that do not require the use of a fan. Such heaters may lack a grill.

As in the embodiment shown inFIG. 1, if any one of the radiation paths between the transmitter and receiver assemblies is interrupted, the heater is preferably shut off and/or the heating elements de-energized. The radiation path must preferably be interrupted for a preselected time duration before the heater shuts off. While the heater could be shut off following a momentary interruption, such an arrangement is not preferred.

FIG. 7is a schematic diagram of a fourth embodiment135of a circuit to perform the object sensing function. The circuit135includes a power control portion, which is connected to AC input power pads136,138. Pad136is connected in series with a fuse140, a resistor142, and a capacitor144. The capacitor144is connected to an input of a bridge rectifier, which includes diodes146,148,150,152which rectifies the input AC power supply to a DC power supply. A Zener diode154is connected from the fuse140to pad138and a resistor156is connected in parallel across the capacitor144. The capacitor144and resistor156preferably operate to filter spikes and noise from the input power signal. The Zener diodes158,160are preferably connected in series from an input of the bridge rectifier to pad138and provide a 24 VDC power source. A capacitor162is preferably connected in parallel with the Zener diodes158,162. A 5-volt regulator164is connected to the output of the bridge rectifier and supplies a 5 VDC power supply at its output.

The circuit135also includes a sensor assembly, which incorporates three infrared (IR) LEDs166,168,170, each of which are connected through a resistor172,174,176to the 5 VDC power source, as well as being connected to pin12of a microcontroller178. The sensor assembly also includes 3 infrared receivers180,184, each of which are connected to the 5-volt power supply and a resistor186,188,190, respectively. Each of the resistors186,188,190are then connected to separate inputs pins1-3of a microcontroller178.

The microcontroller178preferably pulses the IR LEDs166,168,170at pin12and obtains an indication of whether the beam of radiation emitted by the IR LEDs166,168,170has been blocked and/or interrupted through receipt of a signal representing the received infrared light on pins1-3. The infrared LEDs166,168,170are preferably pulsed at a predetermined frequency (such as 38 KHZ) transmitted in a predetermined sequence (such as on for 2 seconds, off for 1 second, and on for 3 seconds), and/or transmitted with a predetermined electrical characteristic, such as but not limited to variations in duty cycle, on-time, off-time, intensity, amplitude, and frequency while remaining within the scope of the present invention including.

The microcontroller178preferably determines when the received infrared signal substantially matches that transmitted and, if not, raises an error condition that represents blockage of the beam of radiation, which signals the heating elements to be turned off by the microcontroller178. Entry into the error condition may be delayed for a predetermined period of time such that blockage of the transmitted beam must be more than transitory before the heating elements are turned off. Similarly, if the microcontroller178determines that the received infrared signal substantially matches that transmitted, the error condition is either not entered or, if the error condition is already present, it may be exited such that the heating elements are turned on again following a predetermined period of time after blockage of the beam of light has been removed.

Circuit135also includes a reset and 5 VDC monitoring circuit192, which detects the 5 VDC power supply and provides a reset signal to the microcontroller178in accordance with its electrical specifications. Circuit192includes a transistor194and a resistor196connected from the base to the emitter of the transistor194. The circuit192also includes resistor198connected from the base of the transistor194to ground, a resistor200connected from the collector of the transistor194to ground, and a capacitor202connected from the collector of the transistor194to ground. A resistor204is connected in series between the collector of the transistor194and pin6of the microcontroller178, a diode206is connected in parallel across the resistor204, and a capacitor208is connected from pin6of the microcontroller178to ground.

The state of an on/off switch210, which is connected to the 5 VDC power supply through a resistor212is monitored at pin8of the microcontroller. An audio indicator214or buzzer is connected to pin9of the microcontroller178through a resistor216.

The microcontroller178is preferably able to control energization of the heating elements by action of pin13, which is connected to the series combination of a resistor218, diode220, capacitor222, and resistor224. The diode226is connected across a point between the diode220and the capacitor222and ground. A capacitor228is connected between a point between the resistor218and the diode220and ground. The collector of transistor230is preferably connected to a relay232and the emitter of the transistor230is preferably connected to ground. Thus, the microcontroller178is able to control whether the transistor230is either conducting or not conducting, which selectively energizes the relay232that further selectively energizes the heating elements (not shown). Circuit135also includes a light emitting diode232, which is connected to pin14of the microcontroller178through a resistor234and is preferably used to indicate whether the heater is powered or not.

It will be appreciated that more than one transmitter receiver pair may be incorporated on the heater. One such additional pair could extend from the front wall14near the bottom of the heater while another pair could extend from the rear wall near an air inlet. As discussed above, the present invention may be applicable to other portable consumer appliances where it may be desirable to turn the appliance off if an object is covering an inlet, an outlet, or other element thereof. Other modifications could be made without departing from the spirit of the invention.