Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Reexamination Certificate
2002-01-08
2003-12-09
Toatley, Jr., Gregory J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
C361S111000
Reexamination Certificate
active
06661634
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to an electrical outlet strip and, more particularly, to a combination electrical outlet strip which comprises a transient voltage surge suppression (TVSS) protection device with electromagnetic interference noise blocking capabilities to and from an attached electrical appliance.
BACKGROUND OF THE INVENTION
Many consumer electronic goods used today contain electronic circuitry which includes miniaturized components and electrical contacts which, due to their diminutive size and the materials from which they are formed, are very susceptible to stray electrical energy caused by voltage transients and electromagnetic interference (EMI). Voltage transients typically occur on the incoming electrical power lines and are represented as a surge or spike in the amplitude of the incoming voltage. In a transient situation, large voltage potentials (i.e., significantly higher than normal operating voltage) may be present over a short time period. These voltage transients can severely damage or destroy electrical components or contacts, thereby rendering the electrical equipment inoperative.
EMI is an unwanted electrically transmitted signal that can propagate through electrical equipment and components interfering with their proper operation by altering their normal operating parameters. Examples of EMI interference include noise on the phone line, erratic data bits on a digital transmission, interference lines across a television screen, in addition to numerous other malfunctions. EMI generally appears in two forms: radiated and conducted. Radiated interference (i.e., Radio Frequency Interference, RFI) is interference that travels through the air from a source to a receiving device and is often the by-product of electromagnetic fields around external wiring. Conducted interference is an undesirable electromagnetic signal traveling on a medium such as an AC electrical power line or ‘wire’ which may be conducted into sensitive electronic equipment and cause malfunctions or otherwise affect operation of the equipment. The conducted EMI may originate from a source directly attached to the wire or it may originate as radiated EMI (i.e., RFI) that is received by and propagated along the wire. In this regard, the wire may act as an antenna that is able to transmit and receive RFI. Further, conducted EMI appears in two forms, common-mode and differential-mode. Common mode EMI occurs when unwanted signal(s) consisting of multiple currents flow in the same direction along the conducting wire. Differential-mode EMI interference occurs when unwanted signal(s) consisting of multiple currents flow in opposite directions along the conducting wire. Finally, EMI can occur in either broadband or narrowband frequencies. Broadband interference is interference which has broad spectral energy distribution exhibited over a wide frequency range and is generally a result of sudden changes in voltage or current. Narrowband interference is interference which has its principal spectral energy confined to a specific frequency or frequencies. This type of interference is usually produced by an oscillator circuit which contains energy only at the frequency of oscillation and harmonics of that frequency. In normal usage, the magnitude of the interference will depend on the bandwidth of the receiver used to detect the signals.
An important source of both conducted and radiated EMI is electrical equipment coupled to AC electrical lines such as computers, switching power supplies, and electrical devices which utilize electrical motors, such as refrigerators, air conditioners and treadmills, etc. In addition, these electronic devices can also produce radiated EMI which may be seen in other nearby electrical devices. As noted above, once EMI from an electrical device is conducted into an electrical wiring circuit, the wiring may act as an antenna and “broadcast” the conducted EMI as RFI throughout a structure.
There are generally two different issues present regarding EMI and electronic devices, the EMI given off by a particular device and the EMI received by the device. Over the last several years, consumer electronic devices have become more sophisticated with the use of microprocessors whose functioning requires clean electrical power free of noise and frequency components that can interfere with their operation. Accordingly, these devices have become more susceptible to EMI problems. Susceptibility is defined as the characteristic which causes equipment to malfunction or exhibit an undesirable response when it is subjected to electromagnetic interference voltages or fields.
SUMMARY OF THE INVENTION
It is, therefore, a primary objective of the present invention to provide an apparatus that reduces the introduction of conducted EMI into an AC power system.
It is a further objective of the present invention to provide means to reduce conducted EMI in digital data transfer sensitive frequencies.
The inventors of the present invention have recognized that many currently used consumer electronic appliances and, particularly, motor driven devices produce EMI in a series of impulse spikes which are generally conducted into the AC power system. Further, the inventors have discovered that these EMI impulse spikes are often of such a magnitude that some consumer digital devices cannot function properly even when there is an EMI filter between the digital device and its AC power supply (i.e., outlet). The inventors have recognized that digital data transfer devices are especially susceptible to conducted EMI interference which often results in poor or lost data transfer and/or disconnection. In particular, broadband data transmissions in the frequency range of 25 kHz to 12 MHz such as telephony digital subscriber line (DSL) systems are highly susceptible to EMI interference produced by motor driven appliances. The inventors have recognized that the impulse spikes created by motor driven devices when switched on or off and, in some cases, created continuously as they operate are disruptive to the operation of data transfer devices and that suppression of these EMI impulse spikes from motor driven appliances before they are conducted into an AC wiring circuit is more effective than filtering the AC power as it is received by the digital device.
In light of these recognitions and in line with the above objectives, the present invention embodies an electrical outlet strip apparatus for interconnection between an AC power source and an electrical appliance that provides transient voltage surge suppression for the appliance and substantially reduces EMI to and from the appliance. The apparatus comprises a first input line, a second input line and a ground line which are adapted to be connected to an existing AC source (e.g., AC outlet). The apparatus further comprises at least one electrical connector having a first, second and third conductors connected to the first input line, the second input line and the ground line, respectively. This connector is operative to interconnect an electrical appliance to the apparatus and thus to the AC power source. At least one voltage surge absorption element is interconnected between at least two of the lines for diverting transient voltages, accordingly, this voltage surge absorption element is disposed between the AC power source and the electrical connector(s). Finally, the outlet strip apparatus contains a multi-stage EMI filter interconnected in series with the first and second input line and grounded to the ground line. The multi-stage EMI filter is disposed between the AC power source and the electrical connector such that electricity from the AC power source to the appliance may be filtered and such that electricity returning from the appliance to the AC power system may again be filtered.
As noted above, the apparatus' input lines are interconnectable to an AC power source. In one embodiment the first input line is connectable to an AC power line while the second input line is connectable to an AC neutral line. In this embodiment
Phillips Bruce A.
Roberts, Jr. John A.
Schneider Carlton Francis Scott
Benenson Boris
Marsh & Fischmann & Breyfogle LLP
Qwest Communications International Inc.
Toatley , Jr. Gregory J.
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