Electricity: conductors and insulators – Conduits – cables or conductors – Single duct conduits
Reexamination Certificate
2000-06-12
2002-06-25
Reichard, Dean A. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Single duct conduits
C174S07000A, C174S0450TD, C138S121000, C138S173000
Reexamination Certificate
active
06410852
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to electrical conduit, and more particularly to an electrical conduit that can easily be cut to size on a job site.
BACKGROUND OF THE INVENTION
Electrical conduit (chase) acts as passageway for electrical wires which connect one electrical service box to another. For example, in a residential use the conduit may run from the back of an electrical meter box through a wall of a house and into a circuit breaker or fuse box in the house. The electrical wires run through the conduit from the electric meter to the circuit breaker box.
Electrical conduit is generally made of tubing which is threaded at both ends so that threaded fittings can be threaded onto the ends to secure the electrical service boxes. One type of conduit is threaded only at its ends and is unthreaded between the threaded ends. This may create a problem during installation, because if the distance between the electrical service boxes does not correspond to the length of the conduit, the conduit must be cut to the appropriate length and threaded at the cut end so that the fittings can be threaded onto the cut end. However, this solution requires additional labor and equipment. Alternatively, if an electrician is unable or does not wish to cut the tubing to its proper length, the extra length of tubing ends up inside one of the electrical service boxes. The extra length of tubing crowds the electrical wires and makes wiring difficult within the box.
Another type of electrical conduit is a continuously-threaded metal tube which can be cut to any length at a job site in order to coincide with the distance between two electrical service boxes. Although this type of conduit solves the problem of variable distance between electrical service boxes, the metal conduit is expensive and requires additional labor and equipment to install. Moreover, metal tubing, such as steel tubing, is difficult to cut, and the metal is cut, large burrs are formed at the cut end. The metal burrs prevent threading of threaded fittings onto the cut end. Therefore, the cut end must be deburred so that the threaded fittings can be threaded onto the cut end of the metal tubing.
Additionally, metal tubing causes greater wear on electrical wires as compared to other softer materials. Further, most local codes require grounding (bonding) of the metal tubing. In order to ground the conduit, a bushing of the conduit is connected to a grounded portion of the electrical service box. However, if the metal tubing is not properly grounded, a serious electrical hazard can be created. Since metal is a conductor, electrical shorts of the electrical wiring within the metal may not be adequately contained.
A need therefore exists for an electrical conduit that overcomes the deficiencies and problems associated with the conventional technology noted above. The present invention address that need.
SUMMARY OF THE INVENTION
A conduit for electrical wires includes a length of continuously-threaded Schedule 80 PVC tubing having a first end and a second end, with the tubing being externally threaded from the first end to the second end. The conduit includes a lock nut and a threaded bushing cooperatively threaded onto at least the first end of the tubing.
In one aspect of the present invention, the conduit further includes a second lock nut and a second threaded bushing cooperatively threaded onto the second end of the tubing. In another aspect of the present invention, the tubing has a collar provided on the second end of the tubing.
The present invention also provides a method of providing a conduit for electrical wires between two electrical service boxes. In the method, a length of continuously-threaded Schedule 80 PVC tubing with a length that is greater than a distance between the two electrical service boxes is cut to a length which is slightly greater than the distance between the two boxes. The first end of the tubing is coupled to one of the electrical service boxes by positioning the end of the tubing inside the box and threading a threaded bushing onto the tubing to secure the tubing to the box. The second end of the tubing is coupled to the other electrical service box in the same manner.
Alternatively, the method may be accomplished by inserting the first end of the tubing through a hole in the other of the electrical service boxes until a collar provided on the second end of the tubing abuts an area of the other of the electrical service boxes which surrounds the hole.
One object of the present invention is to provide a conduit for electrical wires which can easily be cut to any length at a job site.
Another object of the present invention is to provide a conduit for electrical wires which can be installed without requiring deburring of cut ends of the conduit.
Still yet another object of the present invention is provide a conduit for electrical wires which does not require grounding of the conduit.
Another object of the present invention is to provide a conduit for electrical wires which does not increase wear on the wires.
Yet another object of the present invention is to provide an inexpensive conduit for electrical wires.
Still yet another object of the present invention is to provide a conduit for electrical wires which safely contains electrical overloads.
Another object of the present invention is to provide a method of providing a conduit for electrical wires between to electrical service boxes which is easy.
Further objects, features, advantages, and aspects of the present invention shall become apparent from the detailed drawings and descriptions contained herein.
REFERENCES:
patent: 4678867 (1987-07-01), Bongard et al.
patent: 5654525 (1997-08-01), Starozik
patent: 5763832 (1998-06-01), Anselm
Reichard Dean A.
Walkenhorst W. David
Woodard Emhardt Naughton Moriarty & McNett
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