Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-11-17
2002-10-29
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C384S151000, C277S380000
Reexamination Certificate
active
06472786
ABSTRACT:
TECHNICAL FIELD
The invention herein resides in the art of bypass vacuum motors. Specifically, the invention relates to bearing protection systems for bypass motors that are utilized with water pick-up vacuum cleaners such as used for picking up spills or water-based carpet cleaners. In particular, the invention relates to a bearing protection system that prevents water or moisture-laden air from contacting a bearing and wherein the protection system does not contaminate the working air used to operate the vacuum system.
BACKGROUND ART
Presently, some types of cleaning equipment are subjected to water or moisture. In particular, wet/dry vacuum cleaners, such as those known as utility vacs and carpet extractors, operate in an environment in which the debris that is extracted from the surface being cleaned is laden in a mixture of air and water. In order to prevent the moisture-laden air from entering the vacuum generating motor, bypass motors are typically used. As is well known, a bypass motor/fan assembly is one in which the working air, generated by a working air fan, is moved by the motor, but is totally isolated therefrom. The motor itself has a separate motor cooling air fan which draws cooling air over the motor's armature and field. In any event, the working air and the motor cooling air take totally separate paths and do not mix—except possibly in an exhaust area.
Bypass motors typically have a working air fan at an end of a motor/fan shaft, with the fan rotating within a fan shell. One end of the fan shell has an air intake, with the circumference or periphery of the shell having a plurality of spaced-apart exhaust apertures or a tangential exhaust tube. The intake aperture communicates with a vacuum chamber in the cleaning device, while the exhaust ports communicate with the ambient air. The fan shell defines a chamber in which the fan rotates. Once that chamber becomes pressurized, the air therein eventually finds it way to the exhaust ports. Accordingly, the working air fan takes the moisture-laden air from the vacuum chamber and disperses it to the ambient air.
It has been found, especially in applications where moisture is prevalent in the working air, that the moisture migrates into the motor housing and causes failures. In particular, these failures typically occur where the shaft is journaled within a bearing. The moisture contacts the bearing and eventually causes lubricating-grease degradation and loss, rust, and which, in turn, causes the bearing to fail and, in turn, the motor shaft to lock up and burn out the motor.
There have been numerous design modifications attempted to prevent moisture from entering the bearing area. One modification utilizes a grease and/or oil-lubricated synthetic rubber seal disposed on the shaft between the airflow path and the bearing. The lubricant is required as the motor shaft typically rotates at very high speeds. But, the moisture-laden air may have a certain amount of very strong detergent that emulsifies the grease, drying out the lubricating material, and attacking the seal so that moisture eventually migrates along the shaft to the bearing. Moreover, the detergent mixes with the lubricating oil and is then exhausted out the ambient exhaust ports, causing dirt spots or oil spots on the floor upon which the cleaner is used. This is quite upsetting to the user and considered a major product failing of the cleaner. Accordingly, use of synthetic rubber seals as a bearing protection system has been found to be somewhat ineffective.
An alternative modification is the use of a spring-loaded carbon-graphite-on-ceramic seal. These are typically only used on speciality lower-speed applications where exhausting ofthe seal-wear-debris is not an issue. As the carbon-graphite-on-ceramic seals wear down, they tend to “dust,” allowing fine, dark debris to potentially stain the area being cleaned.
One of the more effective alternatives for sealing a working air fan from the motor is to use an air seal bearing protection system. This system utilizes a positive pressure in the area of the bearing, such that contaminants that are in the working air path are kept away from the bearing. This system has been proven to enhance overall life of the bearing. In such a system, air enters through a hole in the fan bracket drawn in by a separate fan. This creates a velocity pressure around the lower (fan end) bearing of the motor and keeps moisture away from the bearing during operation. The air enters behind a baffle and, as it exits, the velocity and pressure in that area keeps moisture away from the bearing. A rubber check valve keeps moisture from getting back into the motor in static or non-operating conditions. Although the air seal bearing protection system has been shown to be effective, it requires enlargement and lengthening of the motor housing and, thus, a significant increase in tooling costs.
Based upon the foregoing, it is evident that there is a need in the art for a dry seal—one without an oil-based lubricant—that is long-lasting, effective, and if the seal breaks down, does not expel dust or particulate that damages the surface being cleaned.
DISCLOSURE OF INVENTION
It is thus an object of the present invention to provide a bearing protection assembly for motors.
It is another object of the present invention to provide an assembly used with motors that have a rotating shaft journaled in a bearing, wherein the shaft rotates a working air fan which generates a working air flow that is maintained separate from the bearing and the motor. It will be appreciated that this separation may be accomplished with a fan end bracket that may or may not be coupled to a diffuser.
It is a further object of the present invention to provide an assembly, as above, in which a dry, non-lubricated seal is secured between a clamping member and a support member to significantly increase the useful life of the bearing and, thus, the motor. The inner diameter of the seal will at least frictionally engage the outer diameter of the rotating shaft or related rotating member.
It is yet another object of the present invention to provide an assembly, as above, in which the dry, non-lubricated seal may be made of a material such as expanded polytetrafluoroethylene, which is impervious to water and cleaning materials and, moreover, which does not break down after excessive wear.
It is yet another object of the present invention to provide an assembly, as above, in which the outer periphery ofthe seal is compressed to enlarge the inner periphery ofthe seal to increase contact with the rotating shaft.
It is still another object of the present invention to provide an assembly, as above, wherein the seal is positioned between the bearing and the working air path. The seal may be positioned so that its inner diameter is in parallel or perpendicular contact with the rotating shaft, depending upon which positioning provides the best performance for the motor assembly.
The foregoing and other objects of the present invention, which shall become apparent as the detailed description proceeds, are achieved by a bearing protection assembly for a motor having a rotating shaft, the assembly including a bearing carried on the shaft, the bearing having one side proximal the motor and one side distal the motor, a support member adjacent the bearing's distal side and disposed about the shaft, a clamping member disposed about the shaft, the clamping member and the support member forming an annular cavity about the shaft, and a non-lubricated seal captured in the annular cavity, the seal precluding migration of moisture toward the bearing along the shaft.
Other aspects of the present invention are attained by a motor assembly having a bearing protection system, including a motor having a rotatable shaft, a bracket holding the bearing to the shaft, a clamp secured to the bracket, and a seal captured between the bracket and the clamp, the seal preventing moisture from migrating to the bearing.
These and other objects of the present invention, as well as the advantages thereof o
Finkenbinder David B.
Kirtz Daniel L.
McCauley Daniel F.
Ametek Inc.
Dinh Le Dang
Ramirez Nestor
Renner Kenner Greive Bobak Taylor & Weber
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