Abstract:
Disclosed herein is a receptacle for selectively conducting electric power. The receptacle contains a switch that is normally open to prevent the occurrence of electric shock. An optical prong detector is provided to determine whether both the hot and neutral prongs of a plug have been inserted into the receptacle. The receptacle provides conductance upon determination of insertion of a plug into the receptacle. Additional features include GFI detection, current detection, heat detection, warning lights and an audible alarm. The receptacle includes communication abilities with remote devices to transmit data indicative of the state of the device.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 13/726,608, entitled “SYSTEM AND METHOD FOR MONITORING AN ELECTRICAL DEVICE” filed Dec. 25, 2012, now U.S. Pat. No. 9,172,233, which is a continuation-in-part of U.S. application Ser. No. 12/493,522, entitled “Surveillance Device Detection With Countermeasures” which was filed on Jun. 29, 2009, now U.S. Pat. No. 8,340,252 and a continuation-in-part of U.S. patent application Ser. No. 12/322,733, entitled “Safety Socket” which was filed on Feb. 6, 2009, which claimed the benefit of U.S. Provisional Application 61/063,951, which was filed on Feb. 6, 2008; the disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a receptacle for preventing electrical shock. More specifically, the invention relates to a safety receptacle for distinguishing between a plug connected to the receptacle and another object. 
       BACKGROUND OF THE INVENTION 
       [0003]    Electrical receptacles, also known as sockets or outlets, which in residential applications are commonly found mounted in an outlet box fixed within a wall and attached by terminals to an insulated powerline. The typical powerline used for residential purposes has a line that has three wires, the first conducts the AC power wave, which is commonly known as the “hot”, the second this a return line, commonly referred to as “neutral” and a solid copper conductor commonly referred to as “ground”. 
         [0004]    The face of a typical receptacle has two parallel slots, and a third opening for the ground. Behind each of the slots and the ground is a contact. A plug having two spades, also referred to as prongs, extend from a plug, conducts power by engaging the contacts. When the receptacle is connected to the line and the circuit is energized, the contacts are live. A common concern in the art is electrical shock resulting from insertion of an object into one of the receptacle slots. The art is replete with solutions to the threat of potential electrocution associated with a child inserting a conductive object in the receptacle. 
         [0005]    There are multiple solutions in the art consisting of covers and inserts to prevent electrical shock. However these devices may become damaged and worn from the constant insertion and removal, which may also lead to neglecting their use altogether. In addition, small children may also pry off the covers to discover the mystery that lies beneath. 
         [0006]    One such solution to this problem is the invention disclosed in U.S. Pat. No. 7,312,394, entitled “Protective device with tamper resistant shutters”. The &#39;394 patent discloses a receptacle cover assembly having a shutter. The shutter is movable to an open position by the insertion of at least one plug blade having a predetermined geometry. Although the &#39;394 patent offers a measure of protection, it has no power shut off safety feature, which would prove critical if an object other than a plug blade were able to deceive the device. 
         [0007]    To prevent electrical shock in bathrooms, building codes require the use of ground fault interrupt “GFI” receptacles. In principle, these devices operate by measuring the current difference between the hot and neutral lines. If a threshold difference is reached a switch is opened and conduction to the contacts within the receptacle is terminated. 
         [0008]    One such device is disclosed in U.S. Pat. No. 7,227,435 entitled “GFCI without bridge contacts and having means for automatically blocking a face opening of a protected receptacle when tripped”. The &#39;435 patent discloses an invention which prevents insertion of the prongs of a plug when the GFI circuit is tripped in the event of mis-wiring or a switch failure. When the device is tripped, an arm moves downward causing the contact to open and a blocking member is moved to a blocking position. However, a concern with this system is in the event of a failure, the contact will not open, nor will the blocking member be moved into the blocking position. 
         [0009]    One solution to the failing GFI switch is found in the invention disclosed in U.S. Pat. No. 7,317,600 entitled “Circuit interrupting device with automatic end of life test”. The &#39;600 patent discloses a GFI circuit capable of simulating a ground fault to determine whether the device is working properly. An integrated circuit chip is connected to switch that interacts with the reset button. A user can determine whether the device has failed by engaging the reset button. However, the user still needs to manually test the device to verify that it is working. Furthermore, the device is normally closed, making the contacts “hot” and hazardous. 
         [0010]    Thus, it is desirable to provide a safety socket that can determine whether a plug has been engaged with the load side of the receptacle or if some other object had been placed into one of the slots. Additionally, it is also desirable to provide a receptacle that is normally open until a plug is engaged into the load side. Finally, it is also desirous to provide a receptacle that can communicate the device&#39;s state to external devices. 
       SUMMARY OF THE INVENTION 
       [0011]    A receptacle for selectively conducting electrical power comprises a housing having at least two apertures located on the load side of the receptacle and at least two conductor contacts, where each contact is disposed adjacent to each aperture to permit conduction with a user engageable contact, such as a blade of a plug. A contact detector having an emitter and a pair of detectors is disposed within the receptacle. Each detector emits a first signal to indicate the absence of an engageable contact and a second signal, distinguishable from the first signal, to indicate the presence of an engageable contact. An interrupter circuit having a line side, a load side and a switch is operatively coupled to a source of electrical power at the line side and to the conductor contacts on the load side. A switch is coupled between the line side and the load side to govern the flow of electrical power to the conductor contacts based on the signals from the receivers. The switch is either open or closed. A signal to cause the switch to conduct is received by the switch if the first and second receivers emit a signal indicative of the presence of an engageable contact. 
         [0012]    In one embodiment, the receptacle has a switch that is normally open to prevent the flow of electrical power to the contacts. A microcontroller may be provided to receive signals from the detectors, the microcontroller having instructions to produce a third signal indicative of the presence of two or more engageable contacts in the receptacle and a fourth signal, distinguishable from the third signal, to indicate the presence of less than two engageable contacts in the receptacle. The microcontroller has instruction to transmit one of either a third or fourth signal to the interrupter circuit to cause the switch to open or close. 
         [0013]    In one embodiment of the receptacle, the emitter produces light and the detectors produce a signal indicative of the light level detected. A filtering circuit may be coupled to the output of each detector, and the emitter being modulated to produce a target frequency to pass through the filter circuit, thereby eliminating ambient interference. 
         [0014]    A partition is disposed between the emitter and each of the detectors, where the partition has an aperture to permit light from the emitter to reach the detectors while blocking ambient light or reflected light. 
         [0015]    In one embodiment, a plug is disposed on the line side of the receptacle, where the plug has at least two pins or prongs, where each of the pins is operatively coupled to one of said conductor contacts. 
         [0016]    The receptacle may produce a unique tone signal to identify the receptacle from others. For example, the tone may identify the location of a fault or event, by knowing that a particular receptacle is in a bedroom, for example, the source of a current spike may be identified. 
         [0017]    Additionally, the receptacle may comprise at least one communications conduit for transmitting signals indicative of the condition of the receptacle, the communications conduit selected from the group consisting of a power line, a serial port and a wireless port. Additional features include the addition of a thermal sensor, a current sensor, a pyroelectric sensor, a warning light and an audible alarm. 
         [0018]    Further objects, features and advantages of the present invention will become apparent to those skilled in the art from analysis of the following written description, the accompanying drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  is a front view of one embodiment of the receptacle according to the principles of the present invention, shown connected to a common electrical power line; 
           [0020]      FIG. 2A  is a perspective view of the receptacle of  FIG. 1 ; 
           [0021]      FIG. 2B  is an alternate embodiment of the receptacle of  FIG. 1 , further comprising a plug with pins for mounting in a pre-existing receptacle; 
           [0022]      FIG. 2C  is a sectional view of the receptacle of  FIG. 1 , revealing an embodiment of a prong detector according to the principles of the present invention; 
           [0023]      FIG. 2D  is a diagram of one embodiment of a prong detector according to the principles of the present invention; 
           [0024]      FIG. 3A  is a schematic representation of a pair of prong detectors of  FIG. 2D , revealing the operative elements therein; 
           [0025]      FIG. 3B  is a schematic representation of a pair of filters for filtering out ambient light from the detectors of  FIG. 3A ; 
           [0026]      FIG. 4  is a schematic illustration of a microcontroller employed in one embodiment of the present invention, operatively coupled to a serial port; 
           [0027]      FIG. 5A  is a schematic illustration of an interrupter circuit according to the principles of the present invention, comprising a switch employing four silicon controlled rectifiers to open or close the AC power wave; 
           [0028]      FIG. 5B  is the interrupter circuit of  FIG. 5A , further comprising a power transformer in front of the bridge diode of the power supply; 
           [0029]      FIG. 6  is an illustration of a system of the present invention comprising a safety receptacle in communication with a master control panel; 
           [0030]      FIG. 7  is an illustration of a master control panel according to the principles of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0031]    Referring now to  FIG. 1  a front view of one embodiment of the receptacle  10  for selectively conducting electrical power comprises a housing  11  supported by a strap  7 . Referring now also to  FIG. 2A , a perspective view of the receptacle  10  of  FIG. 1  is shown. The receptacle  10  has a load side  18  and a line side  19 . A typical powerline connects at the line side  19  of the receptacle  10 . The typical residential powerline has a conductor carrying the AC power wave, or hot wire  2 , a return line, also known as the neutral wire  4 , and a solid copper conductor that is tied to ground, referred to as the ground wire  6 . The receptacle  10  is secured to the hot wire  2  at terminal  1 , the neutral wire at terminal  3  and the rounding wire  6  is secured at terminal  5 . 
         [0032]    Referring now also to  FIG. 2B , an alternate embodiment of the receptacle  10  of  FIG. 1  is shown, further comprising a plug  26  with pins  27  extending therefrom for mounting the receptacle  10  of the present invention in a pre-existing receptacle, making the receptacle  10  portable and easy to install. 
         [0033]    At least a neutral aperture  13  and a hot aperture  14  are located within the face  12  of the housing  11 . For a grounded receptacle, a grounding aperture  17  is also present. A plug  8  having prongs  9 , also known as pins or spades, couples to the receptacle  10  at the load side  18 . 
         [0034]    Referring now also to  FIG. 2C , a sectional view of the receptacle  10  of  FIG. 1  is shown. At least two conductor contacts  15 ,  16  are disposed within the receptacle  10 . Each of the conductor contacts  15 ,  16  are disposed adjacent to each of the apertures  13 ,  14 . Specifically, the neutral contact  15  is disposed adjacent to the neutral aperture  13  and hot contact  16  is disposed adjacent to the hot aperture  14  to permit conduction with a user engageable contact, such as a prong  9  of a plug  8 , when inserted into one of the apertures  13 ,  14 . Each of the contacts  15 ,  16  is disposed adjacent to one of the neutral aperture  13  or hot aperture  14 . For example, when the prongs  9  of plug  8  are inserted into apertures  13 ,  14 ,  17  the conductive material of the prongs  9  permit conduction with the hot and neutral contacts  15 ,  16  (the ground contact is not shown). 
         [0035]    Referring still to  FIG. 2C , a prong detector  20  is disposed in the receptacle  10  and includes of an emitter  21  and detectors  22 ,  23 . Each of the detectors  22 ,  23  emitting a first signal to indicate the absence an engageable contact in one of the apertures  13 ,  14  and a second signal, distinguishable from the first signal, to indicate the presence of an engageable contact in apertures  13 ,  14 . 
         [0036]    Referring now also to  FIG. 2D , a diagram of one embodiment of a prong detector according to the principles of the present invention is shown, revealing the operative elements therein. In the preferred embodiment, the emitter  21  produces light and the detectors  22 ,  23  produces a signal indicative of the level of light detected. Partitions  24  are provided to minimize the interference of ambient light on the detectors  22 ,  23 . The partitions  24  each have an aperture  25  disposed therein to permit light from the emitter  21  to reach the detectors  22 ,  23 . Each of the prongs  9  when properly inserted will interfere with light from the emitter  21 , casing a no light or low light signal from the detectors  22 ,  23 . Therefore if both detector  22  and detector  23  indicate a low light signal, a plug is presumed to be coupled to receptacle  10 . As such when the emitter  21 , detectors  22 ,  23  and partitions  24  with apertures  25  are positioned properly, the presence or absence of the user engageable contact such as prongs  9  may be detected. 
         [0037]    Although residential applications have been referenced herein those skilled in the art will immediately recognize that the application of the presence invention may be employed beyond residential and specifically may also employed in commercial and/or industrial applications. Additionally, even though light emitting and detecting methods are specifically disclosed herein, it is intended to be within the scope of the present invention that other means of detecting the presence of plug blades be substituted for the light emitting and detecting methodologies disclosed herein. 
         [0038]    Referring now to  FIG. 3A  a schematic representation of a pair of prong detectors of  FIG. 2D , revealing the operative elements therein is shown. In the present embodiment, the emitter  21  is a light emitting diode “LED”, for example a GaAs infrared emitter and the detectors  22 ,  23  are photodetectors. Each photodetector  22 ,  23  is an infrared phototransistor, which, as more light strikes the phototransistor, the higher the current flowing through the collector emitter leads causing a “high light” signal from the detectors  22 ,  23 . The circuits in  FIG. 3A  act like a voltage divider. The variable current through the resistor causes a voltage drop. 
         [0039]    As a precautionary measure, in the preferred embodiment, the LED is modulated at about 100 kHz to produce a target frequency and then provided to a filtering circuit  30  as shown in  FIG. 3B . Referring now also to  FIG. 3B , a schematic representation of a pair of filters for filtering out ambient light from the detectors of  FIG. 3A  is shown. The signal that leaves the branch of  FIG. 3A  as 5NS_T1N enters the bandpass filtering circuit  30 . The bandpass filter assists in eliminating erroneous signals that could be generated from ambient light by filtering the incoming voltage and therefore only signals energized by the LED which is modulated at about 100 kHz may pass. The output signal of the filtering circuit  30  T1N_D is then provided to a microcontroller identified as IC8. 
         [0040]    Referring now to  FIG. 4 , a schematic illustration of a microcontroller  40  employed in one embodiment of the receptacle  10  of the present invention is shown. The microcontroller  40  is a programmable logic device, and as such, any suitable programmable device may be substituted for the microcontroller  40  employed in the present invention. Microcontroller  40  receives signals produced by the detectors  22 ,  23 . The microcontroller  40  has instructions to produce a third signal indicative of the presence of two or more engageable contacts  8  in the receptacle  10  and a fourth signal, distinguishable from the third signal, to indicate the presence of less than two engageable contacts in the receptacle  10 . The microcontroller  40  transmits one of the third signal or fourth signal to interrupter circuit to cause a switch to open or close. Additionally, microcontroller  40  receives signals from a number of other sensors, including a thermal sensor, current sensor, and a pyroelectric sensor. The output of microcontroller  40  is operatively coupled to number of communication devices located within the receptacle  10 , including warning lights and audible alarms. 
         [0041]    Microcontroller  40  also communicates through other communication conduits, for example, microcontroller  40  is shown coupled to a serial port. Additionally microcontroller  40  may communicate through the powerline or wirelessly, for example the use of a transponder. The ability to communicate externally provides the receptacle  10  with the ability to transfer data about the state of the circuit for storage on location or off-site. This enables the device  10  to report faults in real-time or to demonstrate gradual deterioration of a condition, such as high current or heat, over time. Such information could be crucial in determining the cause of a fire, for example. 
         [0042]    Microcontroller  40  is programmed to command the receptacle  10  to not conduct electricity unless the microcontroller  40  determines that a plug  8  is engaged with receptacle  10  and not merely some other object inserted into one of the apertures  13 ,  14 . This is achieved by determining the presence of two of two blades  9  inserted into the apertures  13 ,  14  by the detectors  22 ,  23 . Accordingly, the normal state of reciprocal  10  is that no power is conducted to contacts  15 ,  16  unless a plug  8  is determined to be connected to the receptacle  10 . 
         [0043]    The output signals from the microcontroller  40 , based on signals from detectors  22 ,  23 , govern the conductive state of the receptacle  10 . Referring now also to  FIG. 5A , a schematic illustration of an interrupter circuit  50  according to the principles of the present invention is shown. The interrupter circuit  50  has a line side, a load side and a switch. The line side is operatively coupled to a source of electrical power, for example a 14-2 wire. The load side is operatively coupled to the conductor contracts  15 ,  16 . A switch is coupled between the line side and the load side to govern the flow of electrical power to the conductor contacts  15 ,  16  based on the signals from the detectors  22 ,  23 . 
         [0044]    The interrupter circuit  50  governs the flow of electrical power to the conductor contacts  15 ,  16  based on the signals received from the detectors  22 ,  23 . The circuit  50  comprises a switch employing four silicon controlled rectifiers to open or close the AC power wave. Each SCR is provided to conduct or not conduct a half wave coming into the receptacle  10 . Ideally only two SCRs should be necessary, however in the event of miss wiring the hot and neutral lines two SCRs are provided on the neutral line as a safety precaution. The output signals are provided to the gate of the SCRs. When the output signals provide voltage sufficient to conduct across the SCRs, the interrupter circuit  50  is conductive. Note that two of the SCRs are in parallel, but flipped. This is because the SCRs only work in one direction. A diode bridge is provided to rectify AC power to DC. Additionally, GFI protection is provided.  FIG. 5B  is an alternate embodiment of the interrupter circuit of  FIG. 5A , further comprising a power transformer in front of the bridge diode of the power supply. 
         [0045]    Referring now to  FIG. 6 , an illustration of a system  90  of the present invention comprising a safety receptacle  10  in communication with a master control panel  60  is shown. The control panel  60  is wired in line with the branches of the breaker box  75  at an input side and the receptacle on the output side. A wireless alert unit  70  provides notification of remote device status from information received wirelessly. The alert unit  70  is adapted to receive information from receptacle  10 , including location information based on the receptacle identifier tone. The alert unit  70  may send a wireless alert to a computer. 
         [0046]    Referring now to  FIG. 7  an illustration of a master control panel  60  according to the principles of the present invention is shown. The master control panel  60  comprises a case  62  containing electronic remote circuit breakers  63  for remotely disconnecting branch circuits. The control panel  60  includes a battery interface  61  for power backup or circuit conditioning. A beeper  59  and security alarm notification  65  provide warning in the event of a hazard. A transceiver  66  is provided for wireless communication with remote devices. Current sensors  67  are provided to measure branch currents which are reported on a display  58 . A manual disconnect switch  68  is provided to terminate power to all downstream branches. 
         [0047]    The foregoing discussion discloses and describes the preferred structure and control system for the present invention. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims, that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined in the following claims.