Power strip with self-contained ground fault circuit interrupter module

A power strip includes a power cord and a plastic casing mounted onto one end of the power cord. A plurality of outlets are disposed in the casing in a side-by-side relationship. A ground fault circuit interrupter (GFCI) is disposed in the casing and electrically connects the power cord to each of the plurality of outlets. The GFCI is self-contained and modular in form and comprises an outlet-free housing and GFCI circuitry disposed within the outlet-free housing. The GFCI circuitry includes an indicator light, a test button and a reset button which fittingly protrude through corresponding openings formed in both the outlet-free housing and the insulated casing. In use, power cord delivers current to each of the plurality of outlets. However, GFCI serves to interrupt the flow of current from the power cord to each of the plurality of outlets upon detecting a ground fault condition in the power cord.

BACKGROUND OF THE INVENTION

The present invention relates generally to a power strip and more particularly to a power strip which provides ground fault protection.

Power strips are well-known and are commonly used in the art to provide a plurality of ancillary outlets for a single conventional wall outlet.

Power strips are typically constructed to include an plastic or metal casing which is at least partially hollowed out so as to form an interior cavity. The casing is mounted onto a first end of a power cable, said power cable including a hot line, a neutral line and a ground line which are all wrapped together by an outer protective sheath. The second end of the power cable is typically in the form of plug which is adapted to connect with a conventional wall outlet.

Each outlet in the power strip includes a first female contact receptacle which is electrically connected to the hot line of the power cable and a second female contact receptacle which is electrically connected to the neutral line of the power cable. Each of the first and second female contact receptacles is disposed within the interior cavity and is accessible through an associated slotted opening formed in the top of the casing. Optionally, each outlet in the power strip may include a third female contact receptacle which is electrically connected to the ground line of the power cable, the third female contact receptacle being disposed within the interior cavity and accessed through an associated opening formed in the top of the casing.

As such, each outlet is adapted to receive the plug of a device, such as an electrical appliance, which receives current from a power source. Specifically, each contact receptacle of an outlet is adapted to receive an associated contact terminal of the plug. As a result, a current path is established between the outlet and the plug, thereby providing the device with the necessary power to operate.

A power switch is commonly mounted onto the casing and electrically connects the hot and neutral lines of the power cord with each of the individual outlets. As such, the power switch allows for manual regulation of the flow of current between the power cord and each of the individual outlets. The power switch may be provided with an internal circuit breaker which monitors the amount of current passing into and traveling out from the individual outlets. Whenever the amounts of incoming and outgoing current passing into and traveling out from a load connected to the power strip exceeds the current rating of the circuit breaker (thereby signifying a dangerous overcurrent condition) or if there is an accidental short circuit in the load, the circuit breaker opens, or trips, thereby instantaneously cutting off the flow of electricity to the load, which is highly desirable.

Power strips are also commonly provided with surge protection capabilities. Specifically, a surge protector is often disposed within the interior cavity of the casing and electrically connects the hot and neutral lines of the power cord with each of the individual outlets. Connected in this manner, the surge protector protects any load connected to the power strip from a power surge occurring at the wall outlet. A power surge (also commonly referred to as transient voltage) is an increase in the voltage at the wall outlet which is above the standard level (e.g., 120 volts). As can be appreciated, subjecting a load to a power surge can potentially damage and/or destroy the load, which is highly undesirable.

Although widely used in commerce, conventional power strips of the type described above suffer from a notable drawback. Specifically, although conventional power strips provide protection from power surges and overcurrent conditions, conventional power strips do not provide protection from ground fault conditions.

A ground fault condition occurs if the current in the hot line and the current in the neutral line have unequal values (e.g., if the hot line connects directly to ground). As will be described further below, a ground fault condition can be extremely dangerous to a person who is in contact with the load. Specifically, if someone accidentally touches (i.e., grounds) the hot line, the current level in the hot line will immediately become less than the current level in the neutral line. However, because the current path from the wall outlet to the load effectively functions as a closed circuit, the current level in the hot line will always adjust to the current level in the neutral line. As a result, once the hot line is grounded, the current level in the hot line will quickly surge to the current level in the neutral line. This surge in current in the hot line can potentially electrocute the person contacting the load, which is highly undesirable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new and improved power strip.

It is another object of the present invention to provide a power strip which provides ground fault protection.

It is yet another object of the present invention to provide a power strip as described above which includes a readily detectable indicator for notifying the user that the power strip has tripped in response to a ground fault condition.

It is still another object of the present invention to provide a power strip as described above which can be manually reset after the power strip has tripped in response to a ground fault condition.

It is yet still another object of the present invention to provide a power strip as described above which can be manually tripped for testing purposes.

It is yet another object of the present invention to provide a power strip as described above which may be mass produced, has a minimal number of parts, includes modular components, and can be easily assembled.

Accordingly, as one feature of the present invention, there is provided a power strip comprising a power cord comprising a hot line and a neutral line, a casing mounted onto said power cord, a plurality of outlets disposed in said casing, and a ground fault circuit interrupter (GFCI) disposed in said casing, said GFCI electrically connecting said power cord to each of said plurality of outlets, said GFCI regulating the flow of current between said power cord and said plurality of outlets.

As another feature of the present invention, there is provided a ground fault circuit interrupter (GFCI) for regulating the flow of current between a power source and a load, said GFCI comprising an outlet-free housing, and GFCI circuitry disposed in said outlet-free housing.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now toFIGS. 1 and 2, there is shown a power strip constructed according to the teachings of the present invention, the power strip being represented generally by reference numeral11. As will be described further in detail below, power strip11is constructed to provide ground fault protection.

Power strip11comprises a power cord13. Power cord13is conventional in construction and includes a hot line15, a neutral line17and a ground line19which are all wrapped together by an outer protective sheath21constructed of an insulated material.

A plastic casing23is mounted onto one end of power cord13. The other end of power cord13is preferably in the form of a male plug (not shown) which can be inserted into a conventional electrical outlet. With the plug inserted into a conventional electrical outlet, electricity delivered into the electrical outlet travels through the plug, along the power cord13and into the various outlets of the power strip, as will be described further below.

Casing23comprises a bottom portion25and a top portion27which can be fixedly secured together by any conventional means (e.g., using screws, through snap-fit engagement between portions25and27, etc.). Secured together, bottom portion25and top portion27together define an interior cavity29into which the primary electric components for power strip11are disposed.

Power strip11comprises a plurality of outlets31disposed in a side-by-side relationship, each outlet31being adapted to receive a conventional, three-terminal electric plug. Specifically, each outlet31includes a hot line female contact receptacle33which is electrically connected to hot line15. Receptacle33is sized and shaped to conductively receive the hot line conductor blade of a standard electrical plug, receptacle33being accessed through a vertical, slot-shaped opening35formed in top portion27of casing23. In addition, each outlet31includes a neutral line female contact receptacle37which is electrically connected to neutral line17. Receptacle37is sized and shaped to conductively receive the neutral line conductor blade of a standard electrical plug, receptacle37being accessed through a vertical, slot-shaped opening39formed in the top portion27of casing23. Furthermore, each outlet31includes a ground line female contact receptacle41which is electrically connected to ground line19. Receptacle41is sized and shaped to conductively receive the ground pin of a standard electrical plug, receptacle41being accessed through a rounded opening43formed in the top portion27of casing23. As can be appreciated, due to its connection to hot line15, neutral line17and ground line19, each outlet31is provided with the necessary current to power a load connected thereto.

It should be noted that the particular construction of each outlet31does not serve as a principal feature of the present invention. Rather, outlets31serve to represent any conventional outlet which is well known and widely used in the art. As such, outlets31could be replaced with any other type of conventional outlet without departing from the spirit of the present invention. For example, outlets31could be in the form of a conventional two-prong outlet (which does not include a receptacle for receiving a ground pin).

As seen most clearly inFIG. 2, a ground fault circuit interrupter (GFCI)45is disposed within casing23. As will be described further in detail below, GFCI45connects hot and neutral lines15and17with each of the individual outlets31. In this manner, GFCI45serves to interrupt the flow of current from power cord13and into each of the individual outlets31upon detecting a ground fault or grounded neutral condition in lines15and17, which is highly desirable.

As will be described further in detail below, two novel features of power strip11relate to (1) the implementation of ground fault circuit interrupter45in power strip11, and (2) the self-contained, modular construction of ground fault circuit interrupter45.

Housing47is constructed of a durable and insulated material, such as plastic, and includes a bottom member51and a top member53which are releasably secured together using screws55or other suitable means (e.g., rivets or snap-in feature). Together, bottom member51and top member53define an interior cavity56which is sized and shaped to receive GFCI circuitry49.

As seen most clearly inFIGS. 7 and 8, bottom member51is an integral piece which includes a substantially flat bottom panel57and a pair of sidewalls59-1and59-2which extend orthogonally up from opposite sides of bottom panel57, thereby providing bottom member51with a generally U-shaped configuration in lateral cross-section. Bottom member51is shaped to include a pair of openings60, one opening60-1being formed at one end61-1of bottom panel57and the other opening60-2being formed at the other end61-2of bottom panel57. It should be noted that the outer surface of bottom panel57is countersunk around each opening60to receive the head of a screw.

A first mounting bracket62-1is formed onto bottom panel57at end61-1and a second mounting bracket62-2is formed onto bottom panel57at end61-2, each bracket62being positioned at the approximate midpoint between sidewalls59. Each bracket62includes a flat support surface63which is spaced slightly up from and lies parallel with bottom panel57, surface63-1extending out and away from end61-1and surface63-2extending out and away from end61-2. Each support surface63is shaped to define a pair of spaced apart mounting holes65which are sized and shaped to receive a device (e.g., a screw, nail, bolt, etc.) for fixedly mounting GFCI45onto casing23.

Each bracket62is also shaped to include a pair of spaced apart support arms67, each support arm67projecting orthogonally up from bottom panel57and extending at an angle parallel with sidewalls59. As will be described further below, support arms67help retain circuitry49in place on bottom member51. A pair of shortened end walls69project orthogonally up from bottom panel57on opposite sides of each bracket62, each end wall69extending at a right angle relative to sidewalls59.

As seen most clearly inFIG. 10, top member53is an integral piece which includes a substantially flat top panel71. Top panel71is shaped to include a first circular opening73, a second circular opening74and a third circular opening75. As will be described further below, each of openings73,74and75is sized and shaped to fittingly receive an associated component of GFCI circuitry49.

A pair of sidewalls76extend orthogonally down from opposite sides of top panel71, thereby providing top member53with a generally U-shaped configuration in lateral cross-section. A pair of spaced apart tabs77are formed onto the inner surface of each sidewall73and project downward away from top panel71. Each tab75includes a longitudinally extending rib78which is substantially circular in lateral cross-section.

A pair of end walls79extend orthogonally down from opposite ends of top panel71, thereby providing top member53with a generally U-shaped configuration in longitudinal cross-section. A threaded boss81is formed onto the inner surface of each end wall79, the free end of each boss81projecting downward away from top panel71.

It should be noted that, with top member53mounted onto bottom member51, top member53and bottom member51together define a pair of lateral slots83on opposite sides of each bracket61, as seen most clearly inFIG. 11. As will be described further below, each slot83is sized and shaped to receive an associated contact terminal of GFCI circuitry49.

GFCI circuitry49represents any conventional GFCI circuitry. As an example, GFCI circuitry49may be of the type disclosed in U.S. Pat. No. 5,757,598, which is incorporated herein by reference.

As seen most clearly inFIG. 6, GFCI circuitry49includes a main printed circuit board85onto which various circuit components are mounted. Each side of main printed circuit board85is shaped to include a pair of semi-circular notches87, each notch87being sized and shaped to fittingly receive an associated rib78from top member53. Furthermore, each end of main printed circuit board85is shaped to include a pair of longitudinally-extending slots89, each slot89being sized and shaped to fittingly receive an associated support arm67.

As such, with GFCI45assembled together, arms67project into slots89to secure GFCI circuitry49securely in place on bottom member51, as seen most clearly inFIG. 9. Furthermore, with GFCI45assembled together, tabs77abut against the inner surface of sidewalls59to secure top member53in place on bottom member51and ribs78project into notches87to secure main printed circuit board85fixed in place in relation to top member53.

GFCI circuitry49also includes an indicator light91which is sized and shaped to fittingly protrude through opening73in top member53when GFCI45is in its assembled form. In use, GFCI circuitry49is designed in such a manner so that indicator light91will illuminate when circuitry49detects a ground fault or grounded neutral condition. Preferably, indicator light91is in the form of a light emitting diode. However, it is to be understood that indicator light91could be in the form of an alternative illuminating device which is well-known in the art without departing from the spirit of the present invention.

GFCI circuitry49also includes a test button93which is sized and shaped to fittingly protrude through opening74in top member53when GFCI45is in its assembled form. In use, the depression of test button93allows the user to trip circuitry49in ensure that GFCI45is providing proper ground fault protection.

GFCI circuitry49further includes a reset button95which is sized and shaped to fittingly protrude through opening75in top member53when GFCI45is in its assembled form. In use, the depression of reset button95serves to reset circuitry49after a trip condition is experienced.

GFCI circuitry49additionally includes four, blade-shaped, terminal contacts97, each contact97being sized and shaped to fittingly protrude through an associated lateral slot83formed between top member53and bottom member51. Terminal contact97-1is designated for electrical connection with the hot line15of the power source (i.e., power cord13). Terminal contact97-2is designated for electrical connection to the neutral line17of the power source (i.e., power cord13). Terminal contact97-3is designated for electrical connection to the hot line of the load (i.e., each outlet31). Terminal contact97-4is designated for electrical connection to the neutral line of the load (i.e., each outlet31).

As can be seen most clearly inFIG. 1, top portion25of casing23includes a first circular opening99, a second circular opening101and a third circular opening103. With power strip11constructed into its assembled form, GFCI45is disposed between top portion25and bottom portion27of casing23in such a manner so that light91protrudes through opening99, test button93protrudes through opening101, and reset button95protrudes through opening103, thereby providing the consumer with suitable access to the necessary components of GFCI45.

A combination power switch and circuit breaker105is preferably disposed within casing23. Combination power switch/circuit breaker105is preferably disposed in the current path between GFCI45and each of individual outlets31. In this manner, power switch/circuit breaker105can be used to: (1) manually regulate the flow of current between power cord13and outlets31(by means of the power switch) and (2) automatically interrupt current passing into outlets31when the current levels passing into and traveling out from outlets31exceeds a predetermined current rating (by means of the circuit breaker). As can be appreciated, the inclusion of combination power switch/circuit breaker105does not serve as a novel feature of the present invention. Accordingly, it is to be understood that any conventional combination power switch and circuit breaker could be used in power strip11without departing from the spirit of the present invention.

As can be appreciated, the self-contained, modular construction of GFCI45provides a number of significant advantages.

As a first advantage, due to its self-contained, modular construction, GFCI45does not need to be manufactured in conjunction with the device into which it is disposed (i.e., remainder of power strip11). Rather, GFCI45could be manufactured independently of the remainder of power strip11. As a result, it is to be understood that GFCI45could be inexpensively and efficiently mass produced and subsequently sold to the manufacturer of any electric device that requires ground fault protection, thereby increasing the range of its potential applications, which is highly desirable.

As a second advantage, due to its self-contained, modular construction, GFCI45can provide open neutral protection (i.e., circuit protection when the neutral line is cut or otherwise opened) whereas traditional GFCIs do not provide open neutral protection.

As a third advantage, due to its self-contained modular construction, GFCI45can be constructed without a relay circuit whereas traditional GFCIs require a relay circuit. The ability to eliminate the relay circuit from circuitry49of GFCI45simplifies the manufacturing process and reduces costs, which is highly desirable.

As noted briefly above, the modular, self-contained construction of GFCI45allows it to be used in a wide variety of potential applications. In particular, GFCI45can be individually manufactured and sold for use in conjunction with any device that receives current from a power source.

Specifically, referring now toFIG. 12, there is shown a fragmentary plan view of a device for receiving electrical power (such as a stake light), said device being constructed according to the teachings of the present invention and identified generally by reference numeral111. Device111comprises a protective housing113which is at least partially hollowed to allow GFCI45to be disposed therewithin. Preferably, housing113includes a first circular opening115which is sized and shaped to enable light91of GFCI45to fittingly project therethrough, a second circular opening117which is sized and shaped to enable test button93of GFCI45to fittingly project therethrough and a third circular opening119which is sized and shaped to enable reset button95of GFCI45to fittingly project therethrough. As such, the consumer is provided with the necessary access to the buttons and displays of GFCI, which is highly desirable. In use, GFCI45connects the load121of device111with a power source123.

The versions of the present invention described above are intended to be merely exemplary and those skilled in the art shall be able to make numerous variations and modifications to it without departing from the spirit of the present invention. All such variations and modifications are intended to be within the scope of the present invention as defined in the appended claims. For example, it should be noted that the particular components which make up the aforementioned embodiments may be interchanged or combined to form additional embodiments.