Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2003-02-21
2004-07-27
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Electrical device making
C029S525010, C439S800000, C439S778000, C439S790000, C439S781000, C439S785000
Reexamination Certificate
active
06766573
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to electric motors, and more particularly to bonding apparatus for electric motors.
Permanent installation of hydromassage bathtubs and equipment associated with the hydromassage bathtubs (e.g., recirculating pumps, lights, heaters, controls, air blowers) generally requires compliance with a number of installation standards. The installation standards may include standards such as those provided by National Electric Code (“NEC”) (e.g., NEC Article 680), Underwriters Laboratories, Inc. (“UL”) (e.g., UL Standard 1795) and local authorities (e.g., municipal statutes that are often based on the national standards provided by NEC and UL). Standards relating to bonding often require that devices or conductive materials (e.g., metal) located within a distance of the hydromassage bathtub or other devices that are covered by the standards (i.e., in the bonding area) be bonded together to form a bonding grid of the bonding area.
The purpose of forming a bonding grid is to eliminate the potential for an electrical energy differential (i.e., shock hazard) in the bonding area. The bonding grid acts as a path of less resistance than does the path of resistance provided by a human and/or an animal (e.g., cat or dog) located in the bonding area. Any stray electrical energy inside the bonding area is therefore conducted through the bonding grid instead of through the human and/or the animal located in the bonding area.
Bonding apparatus for bonding an electric motor to a bonding grid are generally known. Typically, the bonding apparatus bonds the electric motor to a bonding conductor which is part of the bonding grid. The bonding conductor includes a solid eight (or larger) gauge bare copper wire. The conductor generally does not require use of insulation or a conduit because the conductor does not carry electrical energy under normal operating conditions (i.e., the bonding conductor is only utilized when an electrical energy differential is present in the bonding area). Existing bonding apparatus, such as a bonding lug apparatus
10
illustrated in
FIGS. 1A-B
and
2
A-C, require that a bonding conductor
14
be passed through an aperture
18
in a bonding lug
20
and then bonded to the bonding lug
20
by tightening a threaded fastener or screw
22
down upon the conductor
14
such that the conductor
14
is captured between the bonding lug
20
and the bottom
26
of the screw
22
. The screw
22
is threaded into an aperture or opening
28
in the lug
20
. Existing bonding apparatus are commonly formed of copper or copper alloy.
As is illustrated in
FIGS. 2A-C
, the bonding lug
20
may be connected to an electric motor
34
on the housing
38
of the motor
34
using a threaded fastener or screw
42
. When properly installed, the conductor
14
is electrically coupled to the bonding lug
20
and the bonding lug
20
is electrically coupled to the housing
38
. Generally an adequate electrical coupling is formed between the conductor
14
and the bonding lug
20
. The electrical coupling may be formed via direct contact between the conductor
14
and the bonding lug
20
and/or via indirect contact through the screw
22
. The screw
22
is formed of an electrically conductive material and when the screw
22
is tightened down on the conductor
14
an electrical coupling is formed between the conductor
14
and the screw
22
. The screw
22
is electrically coupled to the bonding lug
20
through the interaction between the threads of the screw
22
and the corresponding threads in the aperture
28
of the bonding lug
20
.
The contact between the bottom of the bonding lug
20
and the housing
38
may provide some degree of electrical coupling, however, the contacting surfaces of the bonding lug
20
and/or the housing
38
may include paint and/or other contamination that can diminish such electrical coupling. The paint and/or other contamination may additionally affect the degree of electrical coupling between the screw
42
and the bonding lug
20
as well as the direct contact between the conductor
14
and the bonding lug
20
discussed above.
The screw
42
is utilized to electrically couple the bonding lug
20
to the housing
38
. Typically, the bonding lug
20
includes an aperture (not shown) through which the screw
42
passes and which is only a clearance aperture. Therefore, passing the screw
42
through the clearance aperture does not provide a reliable electrical coupling between the bonding lug
20
and the screw
42
(i.e., the threads of the screw
42
are not electrically coupled to the bonding lug
20
in a fashion similar to the way the threads of the screw
22
are electrically coupled to the corresponding threads of the aperture
40
). If the screw
42
is not electrically coupled to the bonding lug
20
then the bonding lug
20
is likely not electrically coupled to the housing
38
.
Accordingly, existing bonding lug apparatus (such as the bonding lug apparatus
10
) utilize at least one star washer (not shown) (e.g., a star washer located around the screw
42
between the head
50
of the screw
42
and the bonding lug
20
and/or a star washer located around the screw
42
between the bonding lug
20
and the housing
38
). Alternatively, or in addition, the screw
42
can have a serrated head to provide an electrical coupling between the screw
42
and the bonding lug
20
and therefore between the bonding lug
20
and the housing
38
. The threads of the screw
42
generally become electrically coupled to the housing
38
when threaded into the housing
38
, therefore, the coupling that generally presents a problem is the coupling between the screw
42
and the bonding lug
20
. The star washer located between the head
50
and the bonding lug
20
and the serrated head are both designed to increase the reliability of the electrical coupling between the bonding lug
20
and the screw
42
. The star washer located between the bonding lug
20
and the housing
38
is designed to increase the reliability of the electrical coupling between the bonding lug
20
and the housing
38
. Use of the above techniques typically results in a proper installation.
While installing a motor
34
in a bonding area, the efficiency of the installer is important. Currently, the amount of time it takes the installer to bond the motor
34
to the bonding grid (not shown) includes passing the conductor
14
through the aperture
18
and utilizing the above techniques to ensure all corresponding parts are electrically coupled as required. The installer may pass the entire length of the conductor
14
through the aperture
18
or the installer may cut the conductor
14
, pass a portion of the conductor
14
through the aperture
18
and then reconnect the cut portions of the conductor
14
together to form a continuous electrically conductive path. Depending on the amount of time it takes to pass the conductor
14
through the aperture
18
, reconnect the cut portions of the conductor
14
, and/or perform extra electrical coupling steps, the bonding process may require unnecessary time and effort on the part of the installer.
SUMMARY OF THE INVENTION
The invention provides an electric motor having an integrally formed bonding apparatus that allows the installer to quickly and efficiently bond the electric motor to a bonding grid of a bonding area. The integrally formed bonding apparatus is electrically coupled to a bonding conductor of the bonding grid simply by laying the bonding conductor on the housing of the electric motor and tightening down a fastener such that the bonding conductor is captured between the housing and the shoulder of the fastener. The installer does not need to pass the bonding conductor through an aperture, cut and reconnect portions of the bonding conductor to bond the motor to the conductor, or connect a bonding lug to the housing of the electric motor. The speed at which the installer can bond the motor to the bonding grid using the invention saves the installer time and money.
More particularly, a
Lin Chih M.
Long Norman R.
Watkins William J.
A. O. Smith Corporation
Cuda Rosenbaum I
Kenny Stephen
Michael & Best & Friedrich LLP
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