Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-10-20
2003-08-19
Tamai, Karl I. (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S071000, C310S043000, C277S602000, C277S626000
Reexamination Certificate
active
06608414
ABSTRACT:
BACKGROUND OF THE INVENTION
(i) Field of the Invention
The present invention relates in general to a gasket, and particularly to a gasket that is used between an electric motor and a conduit box attached to the electric motor. The gasket provides a liquid tight seal between the electric motor and the conduit box. The gasket also provides a liquid tight seal between motor leads that extend from the electric motor and go into the conduit box and the gasket. Additionally, the gasket allows the conduit box to be detached from the electric motor and rotated to an alternate orientation relative to the electric motor and reattached to the electric motor in the alternate orientation without breaking the liquid tight seal between the motor leads and the gasket.
(ii) Description of the Related Art
Prior art gaskets used to form a liquid tight seal between an electric motor and a conduit box are well known in the art. These gaskets are typically used on electric motors used in food, beverage, or chemical processing plants where the electric motor is constantly exposed to high pressure washdowns or other high humidity or wet environments. These electric motors have a lead opening through which motor leads extend. The conduit box also has a lead opening. The conduit box is adapted to be attached to the electric motor with the conduit box lead opening aligned with the electric motor lead opening so that the motor leads can extend from the electric motor and into the conduit box through the electric motor lead opening and the conduit box lead opening. In the conduit box the motor leads are connected to a power source.
Typical prior art gaskets are made of a flexible and resilient material such as rubber or the like. These gaskets come in a variety of shapes and have opposite first and second surfaces that are generally flat. The gaskets are designed to be placed between the electric motor and the conduit box attached to the electric motor. The gaskets surround the lead opening on the electric motor and the lead opening on the conduit box. The gaskets also have a lead opening that allows the motor leads to pass through the gasket and into the conduit box. When the conduit box is attached to the electric motor the gasket is compressed between the two and forms a liquid tight seal between the electric motor and the conduit box. The compressed gasket prevents liquids from the exterior of the conduit box and the electric motor from entering the conduit box through the conduit box lead opening and from entering the electric motor through the electric motor lead opening.
The gaskets, however, do not prevent liquids from passing from an interior of the conduit box through the conduit box lead opening, through the gasket lead opening, through the electric motor lead opening and into the electric motor. To solve this shortcoming, a silicone sealant is applied to the gasket lead opening after the conduit box is attached to the electric motor. The sealant fills the gasket lead opening and surrounds the motor leads. The sealant also contacts and adheres to the electric motor lead opening and the conduit box lead opening. After curing for approximately 24 hours, the gasket in conjunction with the sealant provides a liquid tight seal between the interior of the conduit box and the electric motor. Because the sealant is in contact with and adheres to the conduit box lead opening and the electric motor lead opening, the conduit box can not be removed from the electric motor without breaking the seal formed by the sealant. When the seal formed by the sealant is broken, the sealant must be reapplied and allowed to cure for another 24 hours before the electric motor can be put into service.
The electric motors are generally cylindrical in shape and the conduit boxes have bottom surfaces that are concave and complementary to the cylindrical electric motors. Because of the concave bottom surface of the conduit boxes, the conduit boxes can be attached to the electric motors in one of two different orientations. The two orientations are 180 degrees apart. The conduit boxes have a power source opening for running a power source to the interior of the conduit box. The power source is connected to the motor leads in the conduit box interior. The power source opening is typically in a side wall of the conduit box. Because the conduit box is attached to the electric motor in one of two orientations, the power source opening will also be in one of two orientations.
In the typical application of the electric motors, the power source that is to be connected to the motor leads is in a fixed position and the orientation of the conduit box power source opening must coincide with the fixed position of the power source. If the orientation of the conduit box power source opening is incorrect, the conduit box must be removed from the electric motor and reattached to the electric motor in the correct orientation. Prior art electric motors with attached and sealed conduit boxes are disadvantaged in this respect because the removal of the conduit box from the electric motor breaks the seal formed by the sealant and requires the sealant to be reapplied and allowed to cure for 24 hours before the electric motor can be placed in service.
What is needed to overcome this disadvantage of electric motors with attached and sealed conduit boxes is an electric motor that has a gasket that allows the conduit box to be removed from the electric motor and reattached in a different orientation without breaking the seal formed by the sealant so that the electric motor does not need a 24 hour curing period before placing the electric motor in service.
SUMMARY OF THE INVENTION
The present invention overcomes shortcomings of prior art gaskets by providing a gasket that is configured and adapted to allow the conduit box to be removed from the electric motor and reattached to the electric motor in a different orientation without breaking the seal formed by the sealant and requiring the reapplication of a sealant and the resulting 24 hour curing period.
The gasket of the invention is configured and adapted to be positioned between an electric motor and a conduit box attached to the electric motor. The gasket forms a liquid tight seal between the conduit box and the electric motor. The gasket has opposite first and second surfaces and a lead opening that passes through the gasket. The gasket lead opening allows motor leads to pass through the gasket and enter the conduit box through a conduit box lead opening. The gasket first surface has a wall that projects outwardly from the gasket first surface and surrounds the gasket lead opening. The wall defines a cavity within the wall that is adjacent the gasket lead opening. A sealant, preferably an epoxy sealant although other sealants may also be used, is positioned in the cavity. The sealant seals closed the gasket lead opening and seals around the motor leads that pass through the gasket lead opening. The gasket and sealant thereby prevent any liquids in the conduit box from entering the electric motor through the gasket lead opening.
The gasket is preferably constructed of a resilient material. The resilient material allows the gasket lead opening to be dimensioned so that the gasket lead opening is stretched open to allow the motor leads to pass through the gasket lead opening. The gasket lead opening thereby holds the motor leads tightly together.
The gasket is positioned on the electric motor so that the gasket second surface is in contact with the electric motor and the gasket first surface is in contact with the conduit box. The gasket wall has a periphery that is dimensioned so that the gasket wall can be inserted into the conduit box lead opening without being constrained by the conduit box lead opening. The gasket wall periphery may be further dimensioned so that the gasket wall does not contact the conduit box lead opening. Alternatively or additionally, the gasket wall may be dimensioned so that the gasket wall projects outwardly from the gasket first surface a distance that enables the gasket
Emerson Electric Co.
Tamai Karl I.
Thompson & Coburn LLP
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