Patent Grant
7898115
Not Applicable
Electrical appliances have become a vital part of virtually every household and business. Common electrical appliances include curling irons, flat irons, hair dryers, air compressors, electric tools, coffee pots, electric cookers, electric blankets, heating pads, computers and the like. Most common electrical appliances are used by homeowners each and every day and often are an important tool used in the home and/or business. Despite the enormous advantages common appliances afford users, there are also disadvantages. Such routine use of appliances often reduces the user's awareness of the operational state of the appliance. Also, users are often distracted or otherwise inattentive to the appliance.
A large percentage of household fires are attributable to inattentive use of electrical appliances. Frequently, such fires are caused by appliances that generate heat, i.e., hair dryers, curling irons, clothing irons, heating pads and the like. According to the U.S. Fire Administration, between 1998 and 2007, there were an estimated 397,650 residential structure fires annually resulting in 3,040 deaths and 14,960 injuries each year. These fires resulted in an average dollar loss of $6,029 million. In 2006, approximately 11.4 percent of those fires were attributable to heating, which includes such heat generating appliances. See www.usfa.dhs.gov, last visited on Feb. 5, 2009.
Another concern when using appliances is the energy usage, and thus cost associated with use. All electrical appliances consume energy. The cost of operating an electrical appliance ranges from several dollars to hundreds of dollars each year, depending on such things as the frequency of use and size of the appliance. Inattentive users frequently forget to turn off an appliance when they are finished using it and therefore the appliance continues to consume, and waste energy which also adds cost to their energy bill.
In recent years, the trend in appliance design has been to include an auto-shutoff feature for at least some appliances which removes power from the appliance after a predetermined time from when the appliance was turned on. However, these additional features add cost and complexity to the appliance design and manufacture. Therefore, many new appliances do not include an auto-shutoff feature. Also, there are a significant number of appliances already in use that were not manufactured with an auto-shutoff feature.
Thus, a need exists for a power supply switch that can be positioned between a power source and the appliance, the power supply switch operating to remove the power from the power source to the appliance after a delay time.
The present invention relates to a power supply switch for automatically removing power from an appliance after a time delay. The power supply switch is separate from the appliance and desirably includes a power input assembly, a power output assembly, and a control circuit. The power input assembly is generally connected to a power source, such as a standard 110 Volt outlet. The power output assembly supplies power from the power supply to the appliance.
The control circuit comprises a switch, a current detection circuit and a timer circuit. The switch is manually resettable and has an open position and a closed position. When manually reset, the switch moves to the closed position to permit power to be supplied from the power source through the power supply switch to the appliance. The current detection circuit senses a current passing through the switch to the appliance when the switch is in the closed position and outputs a signal indicative of the presence of the sensed current. The timer circuit receives the activation signal and automatically activates a timer in response. The timer sends a signal to the switch after a delay time which causes the switch to move to the open position. When the switch is in the open position, the power from the power source is not passed through the switch to the appliance.
In another embodiment of the present invention, the control circuit further includes an alternating current (AC) to direct current (DC) converter connected to the power input assembly. The AC-DC converter converts at least a portion of the power from the power source into a DC voltage which is then used to provide power to the circuitry included in the power supply switch.
In another embodiment of the present invention, the control circuit further includes a Transient Voltage Suppression (TVS) circuit. The TVS circuit operates to remove, or otherwise suppress transient voltages, e.g., voltage spikes and the like, from the power supplied by the power source. Removal or suppression of transient voltages protects the appliance and the power supply switch from damage caused by excessive voltage spikes.
In yet a further embodiment of the present invention, the control circuit further includes one or more timer set switch(es). The timer set switch(es) has one or more preset positions wherein each preset position corresponds to a different delay time. The user of the power supply can use the timer set switch(es) to select the delay time, i.e., the amount of time the switch will remain in the closed position after the detection of current passing from the power source to the appliance.
The advantages and features of the present invention will become apparent to those skilled in the art when the following description is read in conjunction with the attached drawings and the appended claims.
a and 3b are opposite perspective views showing a specific embodiment of the power supply switch constructed in accordance with the present invention.
Throughout this description, the term “power source” is understood to include any device, apparatus or system supplying an electrical signal capable of powering an appliance. For example, but not by way of limitation, a power source can be the standard 110 VAC, 60 Hz, two or three socket plug found in homes throughout the United States. Alternatively, the power source can be embodied in a proprietary system designed to provide a specific operational voltage or frequency to a particular appliance. The power source can also be the DCV signal available in automobiles, or alternatively, as the DCV signal utilized by airline carriers to provide power to passengers wishing to use electronic devices during flight. As would be understood by one having ordinary skill in the art, a power source can take a variety of sizes, configurations and electrical characteristics and still fall within the scope of the term power source as used herein.
Throughout this description, the term “appliance” will be understood to include any electronic device or apparatus which (1) has a plug that (2) utilizes AC single-phase or DC electricity to operate that (3) has a voltage less than 300V and (4) is designed to perform a specific function for household or light commercial use. Such appliances can include, but are not limited to, a toaster, hair dryer, curling iron, lamp, blender and the like.
Referring now to the drawings and in particular
The power input assembly 12, as shown in
The power output assembly 14, as shown in
An example of the control circuit 15 is shown in
For example in a first embodiment as illustrated in
The relay 36 can be implemented using a mechanical, solid state, combination thereof or any equivalent device which is capable of having an open position and a closed position and is able to be controlled by the latch circuit 34. More particularly, the relay 36 is moved from the open position to the closed position in response to the user manually resetting the reset switch 32 and is further capable of moving from the closed position to the open position in response to the latch circuit 34 receiving a signal from the timer circuit 22.
The latch circuit 34 can be implemented as any mechanical or solid state device, or equivalent thereof that is capable of sensing when the user of the power supply switch 10 manually resets the reset switch 32 and outputs a signal to the relay 36 in response thereto which switches the relay 36 to the closed position. Further, the latch circuit 34 is also capable of receiving a signal from the timer circuit 22 and outputting a signal to the relay 36 in response thereto which switches the relay 36 to the open position. As one having ordinary skill in the art would understand, the latch circuit 34 can be implemented in many forms or configurations that perform the functions described above. Such as, for example, a SR Latch (set-reset) can be used to implement the stated functionality.
The current detection circuit 20 operates to sense current passing through the control circuit 15 and then outputs an activation signal in response thereto. Methods of detecting a current passing along a path are well known in the art and will not be discussed in detail herein. It would be understood by one having ordinary skill in the art that common methods can include, but are not limited to, active sensing, e.g., placing a resistor in the current path and then sensing a voltage drop across the resistor. Another common method of detecting current involves the detection of electro-magnetic energy generated by current traveling along a path. Such detecting can be accomplished using a transformer, inductor or like device. However, other methods of detecting current are known in the art and can be used to implement the current detection circuit 20.
In a particular embodiment of the present invention, the current detection circuit 20 can include a comparator 28, as is shown in
The timer circuit 22 receives the activation signal from the current detection circuit 20 and automatically activates a timer in response thereto. In one embodiment, the timer counts for a predetermined delay time and then outputs a signal to the switch 18 when completed. The timer circuit 22 can be implemented using mechanical, analog, digital circuitry or combinations thereof which perform the functions described herein. For example, and not by way of limitation, the timer circuit 22 can be implemented using a well known digital “555” timer circuit. In the alternative, the timer circuit 22 can be implemented using standard analog circuitry, e.g., a resistor-capacitor circuit. As a further alternative, the timer circuit 22 can be implemented using a mechanical device.
In a second embodiment of the present invention, the control circuit 15 can also be implemented using a micro-controller, microprocessor or the like in conjunction with a current sensing device, as described above, and a switch as is also described above. In this embodiment, the switch 18, current detection circuit 20 and timer circuit 22, or portions of each circuit can be implemented using a single microcontroller. For example, the current detection circuit 20 would utilize a sensing method previously described to sense current passing through the power supply switch 10. In this embodiment, the sensing method would output a signal indicative of the sensed circuit to an analog-to-digital function commonly found in micro-controller devices. The micro-controller could perform all, or at least many of the functions previously described with regards to the timer circuit 22, current detection circuit 20 and the latch circuit 34.
Also described herein is a method of automatically shutting off the power supplied from a power source 16 to an appliance 17 using the power supply switch 10 described herein. The method includes the steps of connecting the power input assembly 12 of the power supply switch 10 to the power source 16. Next, the appliance 17 is connected to the power output assembly 14 of the power supply switch 10. Before or after the appliance 17 is connected to the power output assembly 14, a user manually resets the switch 18 to the closed position such that power from the power source 16 can pass, or passes through the power supply switch 10 to the appliance 17 when the switch 18 is in the closed position. The appliance 17 is turned on and, the current detection circuit 20 senses a current passing through the switch 18 of the power supply switch 10 to the appliance 17 and outputs an activation signal indicative thereof. The timer circuit 22 receives the activation signal from the current detection circuit 20 and automatically activates a timer in response. The timer counts, or otherwise delays for a delay time and then outputs a signal to the switch 18 which causes the switch to move to the open position. As would be understood by one having ordinary skill in the art, power is not allowed to pass through the power supply switch 10 to the appliance 17 when the switch 18 is in the open position to automatically remove the power supplied from the power source 16 to the appliance 17.
The power supply switch 10 can also include several optional features as is illustrated in
The control circuit 15 can also include a Transient Voltage Suppression circuit (TVS circuit 26). This TVS circuit 26 can be positioned to detect and reduce and/or eliminate transient voltages from the power source 16. The TVS circuit 26 can be implemented using an array of devices that are designed to react to sudden or momentary overvoltage conditions. One known method of implementing a TVS circuit 26 is by using a zener diode. However, other methods can be used for the TVS circuit 26 without departing from the intent or scope of the present invention.
The control circuit 15 can also include a timer set switch 30. The timer set switch 30 can connect to the timer circuit 22 and operate to permit the user of the power supply switch 10 to select the delay time. More particularly, the user can use the timer set switch 30 to select the duration of the delay time. The timer set switch 30 can be configured with two or more preset positions wherein each position corresponds to a different delay time. For example, the user can use the timer set switch 30 to select a delay time of 30 minutes, 45 minutes, 60 minutes, or any other predetermined delay time. In another embodiment, the timer set switch 30 can be implemented using an analog device, such as a potentiometer or the like. The analog timer set switch 30 is configured with a minimum and a maximum setting which includes any number of settings therebetween. When the timer set switch 30 is implemented using such an analog device, the user of the power supply switch 10 can select a delay time of any length between the minimum and maximum time.
Shown in
Described below is a specific embodiment of the power supply switch 10 constructed in accordance with the present invention. This embodiment is provided as one example of how the power supply switch 10 can be constructed but should not be interpreted as limiting the scope of the invention. As would be understood by one having ordinary skill in the art, the power supply switch 10 described herein is capable of being constructed in other embodiments without departing from the scope and intent of the invention.
As shown in
Voltage transients, on the incoming power (power source 16), are suppressed by the TVS circuit 26, see
Instant-On circuits usually consume currents in the low milliamp range and allow devices to start or turn on quickly without the need for control circuits to warm or boot up due to the fact that these circuits are always on when the appliance 17 is plugged into a powered electrical outlet.
The output of the comparator circuit is connected to the input of the timer circuit 22. When the output of the comparator toggles to a logic high state, the timer circuit 22 begins its timing countdown (delay time). The desired delay time is set by the operator via a sliding switch (timer set switch 30). The timer set switch 30 is preferably marked with intervals of 30, 60 and 90 minutes or other desired timing intervals. The operator should select the desired time set point based on the time required to complete the task performed by the appliance 17 plus a small buffer time to prevent the nuisance disconnection of power to the appliance 17 before completion of the desired task. The output of the timer circuit 22 remains in a logic low state until the timer circuit 22 timer interval equals the set point interval. Once the timer circuit 22 time interval equals the set point interval, the output of the timer circuit 22 generates a positive pulse of approximately 10 milliseconds. This pulse sets the latch circuit 34. Setting of the latch circuit 34 opens the electromechanical relay or de-energizes the solid state relay (relay 36) which disconnects power to the appliance 17.
The reset switch 32 must be depressed to reset the power supply switch 10. This manual reset switch 32 prevents reactivation of the power supply switch 10 in case of a momentary power failure of the electrical mains to the house or business.
From the above description, it is clear that the present invention is well adapted to carry out the objectives and to attain the advantages mentioned herein as well as those inherent in the invention. While one embodiment of the invention has been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed herein and defined in the appended claims.
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