Patent Grant
7642457
1. Field of the Invention
The present invention relates generally to electrical protection devices, and particularly to electrical protection devices with safety features.
2. Technical Background
As those of ordinary skill in the art understand, an electric circuit comprises many different electrical wiring devices disposed at various locations throughout a structure. These devices include outlet receptacles, which may be combined with other wiring devices such as switches, lighting devices and protective wiring devices. Ground fault circuit interrupters (GFCIs), and arc fault circuit interrupters (AFCIs) are examples of protective devices in electric circuits. Each of the aforementioned protective devices have interrupting contacts for breaking the connection between the line terminals and load terminals when the protective device detects a fault condition. The connection is broken to interrupt the load current and thereby remove the fault condition. Fault conditions include those that result in risk electrocution of personnel, or fire. The outlet receptacles are disposed in duplex receptacles, raceway, multiple outlet strips, power taps, extension cords, light fixtures, appliances, and the like. Duplex receptacles may be configured for installation in outlet boxes. Once installed, a faceplate may be attached to the cover of the outlet receptacle or to the junction box to complete the installation.
Most of these devices have line terminals for connection to the power line, and load terminals for connection to a load. The load terminals include receptacle contacts and feed-thru terminals. The receptacle contacts are configured to accommodate the blades of a plug connector, which are inserted to provide power to a load. Feed-thru terminals, on the other hand, are configured to accommodate wires which are connected to one or more additional receptacles, known as a downstream receptacles. The downstream receptacle may include a string of downstream receptacles that comprise a branch circuit of an electrical distribution system.
One safety issue that heretofore has not been adequately addressed relates to the insertion of foreign objects into receptacle openings. In many cases, young children and toddlers insert objects such as paper clips or screwdriver blades into the receptacle contact openings. Unfortunately, this scenario often results in an electric shock, burns, or electrocution.
In one approach that has been considered, the electrical receptacles in the wiring device are equipped with shuttered openings that prevent the insertion of foreign objects into the receptacle contact openings. One drawback to this approach relates to the ineffectiveness of related art designs. If objects are placed into both openings, the shutter will typically operate, exposing the child to a shock hazard. What is needed is a shutter mechanism that only opens when an actual plug is being inserted into the receptacle.
Another drawback to this approach relates to the complexity of related art shutters. Many shutter designs comprise multiple parts and spring elements that are not integrated into a unitary sub-assembly. The cost and time of assembling the shutter mechanism and the space taken up by their multiple parts limit the usage of these designs. Further, automated environments often generate vibrations and mechanical forces that tend to introduce failure modes. What is needed is a unitary protective shutter assembly suitable for use within automated manufacturing processes.
The present invention addresses the needs described above. The present invention is directed to is a shutter mechanism that is configured to open only when an actual plug is being inserted into the receptacle. The shutter of the present invention defeats the insertion of one or more foreign objects into receptacle openings. The present invention is also directed to a unitary protective shutter assembly suitable for use within automated manufacturing processes.
One aspect of the present invention is directed to a protective shutter assembly for use within a cover assembly of an electrical wiring device. The assembly includes a frameless shutter sub-assembly movable between a closed position and an open position. The frameless shutter sub-assembly is configured to move from the closed position to the open position in response to engaging at least one plug blade having a predetermined plug blade geometry. A spring member is disposed within the frameless shutter sub-assembly. The spring member is configured to bias the frameless shutter sub-assembly in the closed position. At least one retainer element is disposed in the frameless shutter sub-assembly. The at least one retainer element is configured to retain the spring member within the frameless shutter sub-assembly. At least one registration member is disposed on the frameless shutter sub-assembly, the at least one registration member being configured to position and align the protective shutter assembly within the cover assembly.
In another aspect, the present invention is directed to an electrical wiring device assembly that includes a cover assembly having at least one set of receptacle openings configured to accommodate a set of plug blades having a predetermined plug blade geometry. The cover assembly also includes at least one cover registration structure. A plurality of receptacle contacts are disposed in the device, each of the plurality of receptacle contacts being in communication with a corresponding one of the at least one set of receptacle openings. A frameless protective shutter assembly is disposed in the cover assembly. The frameless protective shutter assembly is configured to move from a closed position to an open position in response to engaging at least one of the set of plug blades. The plurality of receptacle contacts are accessible to the set of plug blades in the open position. The frameless protective shutter assembly includes a spring member and at least one retainer element configured to retain the spring member within the frameless protective shutter assembly. The frameless protective shutter assembly also includes at least one shutter assembly registration member configured to mate with the at least one cover registration structure.
In yet another aspect, the present invention is directed to a method for assembling an electrical wiring device. The method includes the step of providing an electrical wiring device having a cover assembly including at least one set of receptacle openings configured to accommodate a set of plug blades having a predetermined plug blade geometry. The cover assembly also includes at least one cover registration structure. A frameless protective shutter assembly is provided. The assembly is configured to move from a closed position to an open position in response to engaging the set of plug blades. A spring member is disposed in the protective shutter assembly. The frameless protective shutter assembly includes at least one retainer element configured to retain the spring member within the frameless protective shutter assembly. The frameless protective shutter assembly also includes at least one shutter assembly registration member. The frameless protective shutter assembly is positioned within the cover assembly. The at least one shutter assembly registration member is coupled to the at least one cover registration structure. The frameless protective shutter assembly is disposed within the cover assembly in substantial alignment with the at least one set of receptacle openings.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.
Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of the protective shutter assembly of the present invention is shown in
As embodied herein and depicted in
The lower shutter 20 includes side rails 22 and a base member 23 disposed therebetween. Base 23 has a first hot contact aperture 26 and a neutral contact aperture 24 formed therein. A transverse hot blade contact structure 28 is disposed between rails 22 and spans a portion of the first hot contact aperture 26.
Transverse contact structure 28 includes a spring retainer pocket 280, upper rail guides 282 and blade contact ramp 284. As the name suggests, upper rail guides 282 allows the rails 42 of the upper shutter to slide therebetween, allowing shutter 10 to move between the open position and the closed position. Rail guides 282 also have a rail stop function. Upper shutter rail stop members 420 abut rail guides 282 to prevent upper shutter 40 from disengaging lower shutter 20 due to the force exerted by spring 30 in the closed position.
Transverse contact structure 28 includes a blade detection geometry implemented by hot blade contact ramp 284 and ramp base 286. The hot blade contact ramp 284 is disposed in a central portion of structure 28. Ramp 284 has a predetermined width and includes contoured surfaces that recede into the face of structure 28. Those of ordinary skill in the art will recognize that the contoured surfaces will cause foreign objects having a width that is less than the predetermined width of ramp 284, such as paper clips and the like, to slide off the ramp and strike the base 286. As a result, a perpendicular force relative to the longitudinal axis of base 23 will be applied by the person wielding the object and the object will be blocked. The predetermined width of ramp 284, of course, is selected in accordance with the geometry of a proper plug blade. Those of ordinary skill in the art will understand that the contoured surface of ramp 284 may be of any suitable shape, such as an arcuate shape, a pointed shape, etc.
The upper shutter member 40 includes guide rails 42 having a base member 48 disposed therebetween. As noted above, the guide rails include a stop member 420 that is configured to abut lower shutter rail guides 282 to prevent the shutters (20, 40) from disengaging due to the force exerted by the spring 30. An upper shutter hot contact aperture 44 is disposed in base member 48.
Upper shutter member 40 also includes a transverse neutral blade contact structure 46 disposed at one end thereof. Transverse neutral blade contact structure 46 includes a spring retainer pocket 460, guide rails 42 and, like the lower shutter transverse contact structure 28, a blade detection geometry implemented by neutral blade contact ramp 462 and ramp base 465. The neutral blade contact ramp 462 is disposed at an end portion of shutter 40. In the closed position, neutral blade contact ramp 462 covers the lower shutter neutral aperture 24. Ramp 462 has a predetermined width and includes contoured surfaces that recede into the face of structure 46. Again, those of ordinary skill in the art will recognize that the contoured surfaces will cause foreign objects having a width that is less than the predetermined width of ramp 462, such as paper clips and the like, to slide off the ramp and strike the base 465. As a result, a perpendicular force relative to the longitudinal axis of base 465 will be applied by the person wielding the object and the object will be blocked. The predetermined width of ramp 462 is selected in accordance with the geometry of a proper plug blade. Those of ordinary skill in the art will understand that the contoured surface of ramp 462 may be of any suitable shape, such as an arcuate shape, a pointed shape, etc.
The protective shutter assembly 10 includes registration members disposed on the frameless shutter sub-assembly. The registration members are configured to position and align the protective shutter assembly 10 within the cover assembly of an electrical wiring device. The lower shutter includes a lower shutter longitudinal registration members 222 and the upper shutter includes an upper shutter longitudinal registration members 464. As their names suggest, the lower shutter longitudinal registration members 222 and the upper shutter longitudinal registration members 464 are configured to correctly align and position the protective shutter assembly 10 within the cover assembly at a position along a longitudinal axis of the protective shutter assembly. Protective shutter assembly 10 also includes snap-in registration members 220. The snap-in elements, of course, allows the shutter assembly 10 to be snapped, as a unit, into the cover assembly, provided that the lower shutter longitudinal registration member 222 and the upper shutter longitudinal registration member 464 are correctly registered with a corresponding registration structure within the cover assembly.
Note that the protective shutter assembly 10 is characterized by a length (L) that is approximately equal to an inch. In a 15A embodiment, the length (L) is approximately equal to 0.860″. In a 20A device, the length (L) is approximately equal to 1.060″.
Referring to
If a foreign object having a width substantially the same as a hot plug blade is inserted into the hot receptacle opening, the shutter assembly remains closed. The foreign object causes ramp 284, and therefore, lower shutter 20, to move. However, this foreign object insertion does not cause upper shutter 40 to move relative to shutter 20. As a result, the foreign object inserted into the hot receptacle opening strikes lower base member 48 of the upper shutter. On the other hand, if a foreign object having a width substantially the same as a neutral plug blade is inserted into the neutral receptacle opening, transverse structure 46 will move upper shutter 40 but not move lower shutter 20. Accordingly, the lower base member 23 does not move and the neutral aperture 24 (See
Only when the hot plug blade and the neutral plug blade of an electrical plug simultaneously engage ramp 284 and ramp 462, respectively, will the lower shutter member 20 and the upper shutter member 40 move relative to each other from the closed position to the open position. In the open position, the lower hot aperture 26 is aligned with the upper hot contact aperture 44 and, the inward edge of the lower neutral contact aperture 24 is substantially aligned with the outer edge of ramp 462. In this position, the lower shutter 20 and the upper shutter 40 allow the plug contact blades to pass through the protective shutter 10 and engage the contacts disposed in the interior of the electrical wiring device.
In another embodiment, the predetermined electrical plug geometry that opens the shutters may include only some of the characteristics that have been described. The geometry may include just one or more of the following: two plug blades separated by a predetermined distance, plug blades contacting the two blade structures simultaneously, a neutral plug blade having a predetermined width, or a hot plug blade having a predetermined width. Plug blade width will not matter if ramps 284 and/or 462 approach the widths of their respective contact structures.
The movement of the upper shutter 40 and the lower shutter 20 is effected by spring member 30. The spring member 30 is configured to bias the frameless shutter sub-assembly, i.e., lower shutter 20 and upper shutter 40, in the closed position. Spring member 30 is compressed further in the open position and, therefore, opposes movement of the frameless shutter sub-assembly from the closed position to the open position. Accordingly when the electrical plug is removed, the spring moves the frameless shutter sub-assembly from the open position to the closed position. Stated differently, only a single spring is necessary to effect the closed position of the shutter assembly.
As alluded to above, the protective shutter assembly 10 includes a spring retainer mechanism. The spring retainer mechanism includes lower shutter retainer pocket 280 and upper shutter retainer pocket 460. The spring retainer mechanism is configured to retain the spring member 30 within the frameless shutter sub-assembly and substantially prevent the spring member from being separated from the frameless shutter sub-assembly. As those of ordinary skill in the art will appreciate, the protective shutter assembly 10 may be dropped and/or exposed to vibrational and/or mechanical forces during automated assembly. As shown in
Referring to
As shown in
The elevation view in
As embodied herein and depicted in
Cover assembly 50 includes a pair of cover registration structures 560, each including a registration alignment key 58 disposed therein. Each alignment key 58 accommodates a lower shutter longitudinal registration member 222 and an upper shutter longitudinal registration member 464. The position of alignment key 58 ensures that the protective shutter assembly 10 is positioned within cover assembly 50 such that the hot aperture 26, neutral aperture 24, and the ramp structures (284, 462) and base portions (23,48) are correctly aligned with the receptacle openings (52, 54).
Each registration structure 560 includes a registration groove 560 that is configured to mate with snap-in registration member 220 (See
Referring to
As embodied herein and depicted in
When the lower shutter member 20 and the upper shutter member 40 move toward each other when going from the closed position to the open position, stop members 422 slide in the reverse direction in apertures 29, moving toward lower transverse member 28.
As embodied herein and depicted in
Like the 15A shutter assembly, the 20A protective shutter assembly 10 is a frameless mechanism that includes a lower shutter member 20 and an upper shutter member 40. A spring member 30 is disposed between lower shutter 20 and upper shutter 40. The lower shutter 20 includes side rails 22 and a base member 23 disposed therebetween. Base 23 has a first hot contact aperture 26 and a neutral contact aperture 24 formed therein (note that aperture 24 is shaped as a t-aperture to be able to accommodate either a 15A or 20A plug when the shutter assembly is in the open position). A transverse hot blade contact structure 28 is disposed between rails 22 and spans a portion of the first hot contact aperture 26. Transverse contact structure 28 includes a spring retainer pocket 280, upper rail guides 282 and blade contact ramp 284. The blade contact ramp 284 is equipped with a blade detection geometry implemented by hot blade contact ramp 284 and ramp base 286.
The upper shutter member 40 includes guide rails 42 having a base member 48 disposed therebetween. As noted above, the guide rails 42 include a stop member 420 that is configured to abut lower shutter rail guides 282 to prevent the shutters (20, 40) from disengaging due to the force exerted by the spring 30. An upper shutter hot contact aperture 44 is disposed in base member 48. Upper shutter member 40 also includes a transverse neutral blade contact structure 46 disposed at one end thereof. Transverse neutral blade contact structure 46 includes a spring retainer pocket 460, guide rails 42 and, like the lower shutter transverse contact structure 28, a blade detection geometry implemented by neutral blade contact ramp 462 and ramp base 465.
Unlike the 15A shutter assembly, the 20A embodiment includes a slot 25 disposed in the base portion 23 of the lower shutter 20. A 20A shutter member 60 is disposed in the slot 25. The 20A shutter member 60 is operable in conjunction with the upper shutter member 40 and is employed to block a portion of the T-slot receptacle opening in the closed position. The 20A shutter member 60 includes an insert member 62, tooth portion 64, and ramp portion 66. The insert portion 62 is configured to snap into slot 25 but is also slideable along the axis of slot 25. The upper transverse member 46 of shutter 40 includes a cam member 466 that is configured to engage the tooth portion 64. The ramp portion 66 aligns with t-slot opening 54, being configured to engage a portion of a 20A neutral plug blade. The operation of the 20A shutter mechanism 60 will be described below.
In operation, an edge portion of a 20A neutral plug blade initially engages ramp 462. Since the edge portion is aligned to the ramp 462 by t-slot opening 54, the edge portion cannot slide off of the ramp as would a foreign object. Thus the edge portion is able to move shutter 40 toward the open position as it is being inserted. At the same time, cam 466 moves away from tooth portion 64. Since shutter 60 is no longer locked, the side portion of the 20A neutral plug blade engages ramp 66 and urges shutter 60 from “Pos. C” towards “Pos. O” (
Referring to
As embodied herein and depicted in
Turning to
When each individual shutter reaches the end of the feeder line 84, a robotic assembly tool (not shown) takes the shutter assembly 10 from the feeder line 84 and positions it within the cover assembly. The robotic assembly tool is designed and programmed to couple the shutter 10 to cover 50 by mating the shutter assembly registration members (220, 464, 222) to their corresponding cover registration structures (56, 58, 560) as shown in
As embodied herein and depicted in
The ground fault circuitry includes a differential transformer 1102 which is configured to sense load-side ground faults. Transformer 1104 is configured as a grounded neutral transmitter and is employed to sense grounded-neutral fault conditions. Both transformers are disposed in toroid assembly L1. Both (LINE) conductors pass thru the sensors. Differential transformer 1104 senses currents from HOT to GROUND but not HOT to NEUTRAL. Both differential transformer 1102 and grounded-neutral transformer 1104 are coupled to detector integrated circuit 1106. Detector 1106 is powered by a power supply circuit 1108 connected to pin V+ on detector 1106. The detector output, provided on output pin silicon-controlled rectifier (SCR), is connected to the control input of silicon-controlled rectifier (SCR) 1100. Filter 1112, comprising resistor R10 and capacitor C7, low-pass filter the detector output signal. GFCI 100 also includes a snubber circuit 1114 that includes resistor R4 and capacitor C8. Snubber circuit 1114 prevents voltage transients from triggering silicon-controlled rectifier (SCR) 1110.
When SCR 1110 is turned ON, solenoid 1116 is energized, actuating circuit interrupter 1118. Solenoid 1116 remains energized for a time period that is typically less than about 25 milliseconds. Circuit interrupter 1118 trips, resulting in the line terminals being disconnected from respective load terminals. After the fault condition has been eliminated, the circuit interrupter 1118 may be reset by way of reset button 132. In one embodiment, the reset mechanism actuated by reset button 132 is purely mechanical in nature and does not include any electrical contacts for test initiation.
GFCI 100 addresses certain end of life conditions by denying power to the load when the device is unable to function. As an example of an end-of-life condition, solenoid 1116 is susceptible to burn-out if SCR 1100 becomes shorted out, or is permanently turned ON. Solenoid 1116 may burn out if it is energized for more than about 1 second. Once the solenoid 1116 burns out, the circuit interrupter 1118 is incapable of being tripped. Solenoid burn-out prevention is provided by auxiliary switch 1122.
Auxiliary switch 1122 is configured to open when the circuit interrupter 1118 is in the tripped position. If SCR 1110 is shorted out, or permanently ON, auxiliary switch 1122 ensures that solenoid 1116 is not permanently connected to a current source. The user may attempt to reset GFCI 100 by depressing the reset button 1120, but the circuit interrupter 1118 will immediately trip in response to the current flowing through the solenoid 1116. Because the trip mechanism 1118 is coupled to the auxiliary switch 1122, auxiliary switch 1122 is opened before solenoid 1116 burns out.
Another failure mode that is addressed by GFCI 100 relates to the end-of-life failure mode of movistor (MOV) 1124. MOV 1124 is disposed in series with auxiliary switch 1122 and trip solenoid 1116. This arrangement significantly reduces the probability of damage due to an over-current situation. When MOV 1124 reaches end-of-life and shorts out, trip solenoid 1116 is energized and auxiliary switch 1122 is opened. As previously described, when auxiliary switch 1122 opens, the flow of short circuit current is terminated before any damage to GFCI 100 ensues.
GFCI 100 also includes trip indication circuit 1126. Trip indicator 1126 is implemented by placing LED1 and series resistors (R11-R14) in parallel with auxiliary switch 1122. LED1 is configured to emit a visual signal when circuit interrupter 1118 and auxiliary switch 1122 are in an open state (tripped).
GFCI 100 also includes a test circuit 1128. The test circuit 1128 is coupled between the line neutral terminal 1282 and the hot receptacle terminal. The test circuit includes a test button 130 disposed in series with test resistor R1.
Finally, GFCI 100 is equipped with a miswire circuit 1150. If an installer improperly connects the load terminals (1260, 1262) to a source of AC power, the miswire circuit 1150 generates a differential current that is detected in accordance with the procedures outlined above. The device 100 continues to trip out until the installer properly wires the device. When the device is properly wired, current flows unabated through miswire circuit 1150, whether GFCI 100 is tripped or not. Fuse S2 is designed to open-circuit after a predetermined period of time. Thus, miswire circuit 1150 is disabled once the GFCI 100 is correctly wired.
Reference is made to U.S. patent application Ser. No. 11/531,588, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of the GFCI circuit.
In one embodiment of the present invention, dimension ‘a’ is less than or equal to one (1.00) inch. The major rearward surface occupies at least 80% of the overall rear surface. In one embodiment, the mounting ears 706 are made from a non-conductive material. In an alternate embodiment, the mounting ears 706 are the exposed ends of an electrically conductive strap assembly connected to the grounding conductor of the electrical distribution system when the device 100 is installed. The conductive strap is connected to the receptacle ground terminals that accommodate the ground prong of the user attachable plug. The housing depicted in
Linkage assembly 1540 includes two pivot arms 1542, each of which are removably coupled to a protective shutter 10 in the closed position. Cam member 1544 is coupled to pivot arms 1542, by way of pivots 15440. The cam member 1544 is configured to rotate around an axis of rotation to thereby move the pivot arms 1542 in the linear direction as shown. Rotor 1546 is coupled to cam 1544 at one end, and is also coupled to circuit board 1000 at an opposite end. A torsion spring assembly 1548 is coupled to rotor 1546. Spring assembly 1548 includes torsion spring 15480 which is coupled to the miswire circuit 1150 disposed on the other side of circuit board 1000.
In the locked position, torsion spring 15480 is in tension, and stores mechanical energy. When miswire circuit 1150 senses the proper wiring condition, it releases spring 15480, allowing it to move within slot 102. The stored mechanical energy is released, causing rotor 48 to rotate cam 46 about the axis of rotation. In response, each pivot arm 42 is moved in a linear direction as shown. In one embodiment of the present invention, torsion spring 15840 is held in place by a fuse element (S2) that is configured to open-circuit after current is applied for a predetermined period of time. The operation of the miswire circuit 1150 and fuse S2 was discussed above in detail.
Reference is made to U.S. Pat. No. 6,969,801 and U.S. patent application Ser. Nos. 10/729,685 and 10/900,788, which are incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of the tamper resistant shutter mechanisms.
AFCI 90 is formed from components that are readily available and that can be easily integrated into an electrical receptacle, plug, or in-line device. The circuit is designed so that it can be manufactured in the same form as ground fault circuit interrupter (GFCI) receptacle devices. AFCI 90 protects an electrical circuit which includes at least a neutral conductor 900 and a line conductor 901 connected to a power source (not shown). A ground conductor (not shown) is optionally present. AFCI 90 detects electrical arcs occurring between line conductor 901 and ground, neutral conductor 900 and ground should the power source be of reverse polarity, or line conductor 901 and neutral conductor 900.
A circuit interrupter 902 is connected in series with line conductor 901 between the power source and a load 99. This embodiment incorporates a first stage arc sensor 920, shown as a current transformer, which is configured to respond to the rate of change of neutral and/or line conductor current with respect to time. Sensor 920 may be designed with a physically small core of a type and number of secondary turns which gives optimum sensitivity during arcing. Either a single conductor (LINE) or both conductors can pass thru the sensor. The arc fault detector detects arcs that are either LINE to GROUND or LINE to NEUTRAL. Sensor 920 feeds two detector/amplifiers 921, 922. Detector/amplifiers 921, 922 are preferably RV4141A (Fairchild Semiconductor) low power ground fault interrupter ICs. Detector/amplifier 921, also referred to as the di/dt stage, has a high pass filter capacitor 911 on its input side, while detector/amplifier 922, also referred to as the 60 Hz or “threshold” stage, uses a low pass filter capacitor 912 in a feedback stage. The 60 Hz threshold detector 922 controls the level at which an arcing condition is to be detected, e.g., at a 75 Ampere or greater load current.
Reference is made to U.S. patent application Ser. No. 11/531,588, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of the AFCI circuit.
Transient voltages are known to occur between any pair of two of these conductors, and surge suppression devices, such as metal oxide varistors, are arranged to absorb transient voltage surges between any pair of the conductors. Fuses are provided for disconnecting the surge suppression devices from the circuit in the event of failure. Two specific failure modes are provided for, over current failure and temperature failure.
A first metal oxide varistor 1016, such as a 150 volt RMS metal oxide varistor is connected in series with a first thermally responsive fuse 18, a second thermally responsive fuse 1020, and a conventional over current fuse 1022, and the series combination is connected between the hot conductor 1010 and the neutral conductor 1012. A second varistor 1024 of the same type is connected at one end 1026 in series with three fuses just mentioned, and the other end 1028 is connected to the ground conductor. These two varistors protect the hot-neutral and hot-ground pairs. Each of the thermally responsive fuses 1018, 1020 is positioned physically close to one of the varistors 1016, 1024, so that a rise in temperature of the varistor, as would be caused by a failure, causes the adjacent fuse to open. Since the two thermally responsive fuses 1018, 1020 are connected in series, the thermal failure of either of the varistors will cause the connection of both varistors to the hot conductor to be broken.
A third metal oxide varistor 1032 is connected in series with another thermal fuse 1034, and an over current fuse 1036. The combination of the third varistor 1032 and the two fuses 1034, 1036 is connected between the neutral conductor 1012 and the ground conductor 1014. A thermal failure or an impedance failure of the third varistor device 1032 will cause one of the thermal fuse 1034 or the over current fuse 1036 to open, thereby disconnecting the varistor from the neutral-ground circuit.
A visible indicator, such as a light emitting diode 1040, is connected between the hot conductor 1010 and the neutral conductor, 1012 so that the light emitting diode 1040 is illuminated when all three of the varistors 1016, 1024, 1032 are functional, more particularly when none of the fuses 1018, 1020, 1022, 1034, 1036 is blown. A half wave rectifier diode 1044 has its cathode 1046 connected to the electrical conductor in series with the two thermal fuses 1018, 1020 and the over current fuse 1022, feeding the first two varistors 1016, 1024. The cathode of the rectifier diode 1044 is connected to one terminal of the light emitting diode 1040. The other terminal of the light emitting diode 1040 is connected through a blocking diode 1050 to a current limiting resistor 52, arranged in series, and then through the third thermal fuse 1034 and third over current fuse 1036 to the neutral electrical conductor 1012. A decoupling capacitor 1056 is preferably connected between the anode of the diode 1044 and the neutral conductor 1012.
When all of the fuses 1018, 1020, 1022, 1034 and 1036 are intact, that is when no fault has occurred, a circuit is created from the hot-conductor 1010 through the rectifier diode 1044, the light emitting diode 1040, the blocking diode 1050, the current limiting resistor 1052 and thence to the neutral conductor. The light emitting diode provides visible indication. If any of the three thermal fuses 1018, 1020, 1034 or two over current fuses opens 1022, 1036, the circuit is interrupted and the light emitting diode is extinguished, alerting a fault condition.
A TVSS 1000 in accordance with this invention also provides an audible indication of a fault in either of the varistors 1016, 1024 protecting the hot-neutral circuit or the hot-ground circuit respectively. A device, such as a simple buzzer 1060 or a piezoelectric device, has one terminal 1062 connected to the hot conductor 1010, and the other terminal 1064 connected by way of the series combination of a zener diode 1066, a current limiting resistor 1068, a first blocking diode 1070, second blocking diode 1050, second current limiting resistor 1052, the thermal fuse 1034, and the over current fuse 1036 to the neutral conductor 1012. The first and second thermal fuses 1018, 1020 and the first over current fuse 1022 are connected in series with rectifier diode 1044 and the light emitting diode 1040 between the hot electrical conductor 1010 and the junction of the two blocking diodes 1070, 1050 just mentioned, so that in normal operation no significant voltage passes through the buzzer, and the buzzer remains silent. If either of the varistors 1016, 1024 bridging the hot-neutral or hot-ground fails and any of the first and second thermal fuses 1018, 1020 and the first over current fuse 1022 is opened, voltage across the buzzer 1060 will cause it to sound.
In order to allow a user to deactivate the buzzer while awaiting repair, a normally open switch 1072 is connected effectively across the combination of the buzzer 1060 and the zener diode 1066. When the switch 1072 is closed, current through the buzzer 1060 is shunted through the switch and the buzzer is silenced. A capacitor 1074 is provided across the zener/audio alarm network to provide a DC voltage component to improve the audio alarm operating performance.
The buzzer deactivating switch 1072 is a simple normally open electrical switch, rather than a device that permanently deactivates the alarm 1060 or permanently interrupts a circuit trace. The switch 1072, once closed, can be opened at will and the buzzer 1060 reactivated. Accidentally deactivating the buzzer might destroy the audible alarm feature of the device permanently, and require its replacement even before it is installed. The use of a normally open switch in accordance with this invention eliminates this problem, and allows the alarm to be deactivated and reactivated.
Reference is made to U.S. patent application Ser. No. 11/531,588, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of transient voltage surge suppressor (TVSS) wiring device.
Referring to
In one embodiment, the GFCI receptacle is independent of the single pole switch 105. The load terminals of the GFCI receptacle may be electrically connected to the line terminals of the single pole switch 105. Thus, switch 105 is protected by the circuit protection components of GFCI 100-1. When GFCI 100-1 sense a fault condition, the GFCI trips in the manner described above, and no power is supplied to the switch 105. The electrical wiring device may further include a trip indicator 1314 mounted in and visible through the cover 50. The trip indicator 1314 may be implemented using an LED, a neon source, or other suitable light source.
Reference is made to U.S. patent application Ser. No. 10/994,662, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of a GFCI/Switch combination device.
Referring to
The night light portion includes a lens cover 110. As those of ordinary skill in the art will appreciate, lens cover 110 may be fabricated using a clear or translucent material in accordance with factors such as light source type, emitted wavelength, desired light intensity, desired light diffusion characteristics, etc.
In one embodiment of the present invention, lens cover 110 may be removable to provide access to the light source. Lens cover 110 has a height (H) less than or equal to approximately 0.8 inch and a width (W) that substantially equal to the width of cover assembly 50.
Reference is made to U.S. patent application Ser. No. 10/998,369, which is incorporated herein by reference as though fully set forth in its entirety, for a more detailed explanation of a GFCI/Night Light combination device.
As embodied herein and depicted in
Raceway structure 2100 includes a cover member 2150 that is configured to mate with a body member 2110. Cover member 2150 includes snap-in members 2156 that are configured to mate with openings 2112 disposed in body member 2110. Cover member 2150 also includes receptacle openings 2152, 2153, and 2154, to accommodate the hot plug blade, ground plug blade and neutral plug blade, respectively, of a plug device.
The raceway body member 2110 includes a shutter registration pocket 2120. The shutter registration pocket 2120 includes a hot contact opening 2122 that is aligned with hot cover receptacle opening 2152. The hot contact opening is configured to receive hot contact 2132 therein. Pocket 2120 also includes a neutral contact opening 2124, the opening 2124 being aligned with neutral cover receptacle opening 2154. The neutral contact opening 2124 is configured to receive neutral contact 2134 therein. Pocket 2120 further includes a ground contact opening 2123 aligned with ground cover receptacle opening 2153. The ground contact opening 2123 is configured to receive ground contact 2133 therein.
As its name suggests, the shutter registration pocket 2120 is configured to accommodate protective shutter assembly 10 (shown in an exploded view in
As embodied herein and depicted in
The bottom portion 2204 also includes registration members (not shown for clarity of illustration) spaced at appropriate positions along the longitudinal axis of the bottom portion 2204. The bottom registration members are configured to receive hot contact 2252, neutral contact 2254, and ground contact 2253 at each position along the longitudinal axis of the bottom portion 2204. Of course, those of ordinary skill in the art will understand that these positions are aligned with the locations of the receptacle openings formed in top portion 2202.
The raceway structure 2200, therefore, is assembled by coupling the top portion 2202 to the bottom portion 2204 such that a shutter assembly 10 is disposed between each set of receptacle openings disposed in the upper portion 2202 and a corresponding set of contacts disposed in the lower portion 2204.
Raceway structure 2200 commonly has an interior width dimension denoted in
A multiple outlet strip (MOS) is similar to raceway except that it is typically shorter in length. It may be provided with an electrical plug and its receptacle outlets may be more tightly clustered in a row or even disposed in more than one row. Despite these differences, the receptacle outlets in an MOS can be configured to include the shutter mechanism assembly such as in the manners described for raceway.
Referring to
As embodied herein and depicted in
Ground shutter assembly 70 is configured to snap into a registration pocket (not shown for clarity of illustration) disposed inside the front cover 50 of the receptacle. The registration pocket aligns the ground shutter blade opening 76 with the ground receptacle opening 53 (See
The ground blade shutter affords several benefits. When a ground blade is not present, shutter 70 is in the closed position such the slide shutter 74 blocks ground shutter blade opening 76. One benefit is that ground shutter 70 prevents contaminants, insects and other such undesirable materials from entering the wiring device. Another benefit is that when a ground blade is not present, the hot and neutral shutters in shutter assembly 10 are locked in the closed position by lockout arm 12. Lockout is maintained even if there is an attempt to insert an electrical plug having hot and neutral blades. This prevents an ungrounded plug (or a plug with a missing ground blade) from receiving electrical power.
Referring to
As shown in
Referring to
Referring back to
Referring to
A ground blade shutter may be particularly useful in duplex receptacles having an isolated ground configuration. The aforementioned isolated ground configuration refers to a receptacle device having mounting straps that are electrically isolated from the ground contacts.
Referring to
All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.
The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening.
The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein.
All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed.
No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
This is a continuation of U.S. patent application Ser. No. 11/609,793 filed on Dec. 12, 2006, which is a continuation-in-part of U.S. patent application Ser. No. 10/900,778 entitled “A Protective Device with Tamper Resistant Shutters” filed on Jul. 28, 2004, which is a continuation-in-part of U.S. patent application Ser. No. 10/729,685 entitled “A Protective Device with Tamper Resistant Shutters” filed on Dec. 5, 2003, the contents of which are relied upon and incorporated herein by reference in their entirety, and the benefit of priority under 35 U.S.C. §120 is hereby claimed.
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| Number | Date | Country |
|---|---|---|
| 2004066327 | Aug 2004 | WO |
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| Number | Date | Country | |
|---|---|---|---|
| 20090052120 A1 | Feb 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11609793 | Dec 2006 | US |
| Child | 11933928 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10900778 | Jul 2004 | US |
| Child | 11609793 | US | |
| Parent | 10729685 | Dec 2003 | US |
| Child | 10900778 | US |
