Electrical connectors – Metallic connector or contact having movable or resilient... – Screw-thread operated securing part
Reexamination Certificate
2001-02-02
2002-12-24
Abrams, Neil (Department: 2839)
Electrical connectors
Metallic connector or contact having movable or resilient...
Screw-thread operated securing part
C439S797000, C439S718000
Reexamination Certificate
active
06497592
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a connector assembly for a transformer box for providing power to multiple output devices and more specifically to a transformer box having connection blocks to facilitate connections with improved safety and accessibility.
BACKGROUND OF THE INVENTION
Environmental lighting systems typically operate by providing low voltage to a number of lamps which are positioned to enhance various features in the environment, such as buildings, statues or trees, or to illuminate walkways or open areas for safety. The low voltage, usually 12 volts, is produced by one or more transformers that are connected to a 120 VAC source and positioned within the area covered by the lighting system in a way to ensure a supply of stable voltage levels as well as to operate efficiently. An important consideration when designing a lighting system is light output and lamp life, both of which are optimized when each lamp is operated within a relatively narrow voltage range, e.g., 10.5 to 11.5 volts. Because the light fixtures are usually positioned at varying distances from the transformer box with differing numbers of fixtures on different cables, the voltage requirements for any given cable may differ. Cables to lamps at the greatest distance from the transformer and/or having a greater quantity of lamps will require an initially higher output voltage and/or a heavier gauge of cable to compensate for voltage drop over long stretches of cable and multiple lamps. The physical size of the cable on the 12 volt secondary side can become very large when a cable run requires a high wattage load, such as would be needed for a long path or driveway. Basic electrical theory dictates that the cable conductors on the 12 volt side of the transformer will be much larger than the conductors on the 120 volt primary side. In order to reduce the supply voltage down to a safe 12 volts, the amperage must be increased by a factor of ten. In theory, the cable gauge to carry 300 watts at 12 volts (25 amps) should be 10 times the thickness of the cable from the 120 volt source (2.5 amps.) To correctly account for this relationship, the low voltage connector in a terminal box should be able to accommodate large gauge cables. In conventional outdoor lighting systems, however, this is not the case, and the available connectors do not provide adequate physical openings to securely receive large gauge cables. Another consideration in the lighting system design is centering of the wattage load in order to minimize cable runs, also to avoid excessive voltage drops for efficient use of the supply voltage.
Most existing transformer boxes were designed and built for industrial applications. Although the basic functionality of a transformer box has not changed for many years, there is now a heightened awareness of safety and visual accessibility issues that exist when they are used in a public, commercial, or residential setting, such as in environmental lighting systems. An aspect of environmental lighting systems that creates a particular safety issue is the aforementioned need to center the transformer within a lighting zone for balanced distribution of power. This means that the transformer may be located in a position that is not as easily secured as might be, for example, a service cabinet or closet on the side of a building or garage. Thus, while efforts are usually made to locate the transformer inconspicuously, outside of direct view, they may, nonetheless, be accessible to individuals, including children. Thus, it is important to ensure that wires leading to and from the transformer be firmly secured.
Lighting systems are typically installed by professional installers who will need ready access to the transformer's interior connection points. In existing systems, these connection points are often plastic conduit sleeves into which the bare cable wire is inserted and held in place by a flat-top set screw. Set screws are located within a covering made of plastic or other insulating material to prevent inadvertent contact with metal which may be conducting electricity. In a typical low voltage lighting installation, there are several field cables running into a single terminal connection. It can be difficult for the installer to insert the large gauge, often-times stiff wires into the narrow openings. Further, the set screws, which are fairly small, are recessed within the protective material, so the screwdriver must be inserted into an opening in the plastic, making clear visual confirmation of the connection difficult. Most terminal connectors are of a blind type which do no allow the installer to visually confirm the connection by seeing the conductors pass under the set screws. Without a solid connection, arcing and overheating can occur. Although the voltage may be low, the current can be as high as 50 amps. Loose or inadequate metal-to-metal connection with the field wire can be particularly hazardous since the circuit protection in the transformer or main house circuit breaker will not detect an overheated terminal connection because it does not cause a short or an excessive amperage to trip the breaker.
Since the installer is generally well-versed in safe handling of electrical conductors, and since he or she will be doing most of the installation with the system disconnected from a live voltage supply, safety concerns are not as much of an issue as they might be for the uninitiated homeowner or curious child after the lighting system is operational. Thus, the installer may consider the conventional safety features to be obstacles to making secure connections. Regardless of inconvenience to the installer, safety precautions must be taken to avoid accidental electric shock once the 120 VAC is connected.
For the reasons described above, there remains a need for a transformer box construction that allows for easy and secure connection of a lighting system in the smallest-possible physical size enclosure while providing protection against electrical shock for untrained persons who may intentionally or unintentionally gain access to the interior of the transformer box.
SUMMARY OF THE INVENTION
It is an advantage of the present invention to provide a transformer box connector that allows for easy and secure insertion of electrical wires.
It is a further advantage of the present invention to provide a transformer box connector with a hinged cover that protects against direct contact with bare wire or an exposed connector after the system is operational, thereby helping to limit the possibility of severe injury from electrical shock.
Another advantage of the present invention is to provide a transformer box connector that is safe, compact, and simple-to-use.
Yet another advantage of the present invention is to provide a terminal connector that provides means for visual confirmation of a connection.
In an exemplary embodiment, the transformer box connector is encased within a transformer box. The transformer box has a hinged door and an interior volume for retaining a transformer housing. A transformer and other components can be located underneath the housing. The hinged door includes a lip which attaches to the latching mechanism mounted on the side of the transformer box for securing the hinged door. The transformer box will preferably be made of a stainless steal or other similar material so the transformer box will be protected from outside elements. The transformer box is supplied standard household power of 120 VAC via an electrical cable or power cord.
In an exemplary embodiment, the transformer box connector comprises a terminal block retainer mounted on a housing located in the interior of the transformer box. The terminal block retainer has a hinged cover that is pivotally attached at the rear corners of the terminal block retainer. In one embodiment, the hinged cover can be lifted and slide downward from the top of the rear corners so that the hinged cover will be locked into place. In another embodiment, the hinges are configured to provide a catch or lock which allows
Abrams Neil
Kilpatrick & Stockton LLP
Musick Eleanor M.
LandOfFree
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