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Method and structure for cooling an electric motor

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Method and structure for cooling an electric motor


A high speed electric motor for use in a variety of applications. The electric motor an electric motor including a motor housing or stator, a rotor having a commutator and brushes for contacting the commutator at a predefined area known as the contact area. Additionally, the motor includes a forced air cooling assembly. The forced air cooling assembly includes a centrifugal fan for creating air flow, a manifold for accelerating the air flow. The manifold having exit ports and the exit ports being positioned directly over the contact area for directing the accelerated air flow at the contact area and the motor housing having at least one opening aligned with the contact area and at least a second opening defining an exit vent. Additionally, a method of cooling the motor in accordance with the invention is also disclosed.
Related Terms: Brushes Centrifugal Fan High Speed Motor Housing

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USPTO Applicaton #: #20140042867 - Class: 310227 (USPTO) -


Inventors: Wing-kin Hui

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The Patent Description & Claims data below is from USPTO Patent Application 20140042867, Method and structure for cooling an electric motor.

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REFERENCE TO RELATED APPLICATION

This application is a continuation of Ser. No. 13/103,301, which has now been allowed and which shall issue as patent in due course. That application is a continuation of U.S. Pat. No. 7,804,208. Other than this paragraph, the only changes made to the application as originally filed are those set forth in Response A of the parent case with respect to the section “In the Specification” as well as certain typographical errors which have been corrected. No new matter has been added.

FIELD OF THE INVENTION

This invention generally relates to the field of brushed electrical motors. More particularly, this invention relates to small, high speed electric motors, which include structure for internal cooling.

BACKGROUND OF THE INVENTION

Electric motors are in widespread use for a seemingly never ending variety of tasks. Such motors are popular because they are small and powerful. Additionally, there is virtually zero pollution and generally speaking the motors run far more quietly than other motors, such as an internal combustion engines (ICEs). Many industries rely solely upon such electrical motors to power their devices. For example, pool cleaners are virtually exclusively powered by such motors. As will be appreciated, in order to make such devices practical, the motors must be quite small and very powerful. Such motors are required to rotate at extremely high speed and are placed in a confined spaces. As will be readily understood the physical limitations of such spaces and the high speed of the motors means that heat build up can be extreme, especially when such motors are put to constant and heavy usage.

The two weakest points to such small high speed electric motors in a confined space are heat which catastrophically damages the copper windings of the motors and dust or particulate matter build up on the commutator, especially at the contact area between the brushes and the commutator which likewise causes catastrophic failure. Heat causes the Copper wiring of the armature to become so hot it fails to function and then fails catastrophically so that the motor is permanently damaged and needs to be replaced. Thus, heat is the primary enemy of such motors and there is a long felt need to cool such motors.

Next is dust or particulate matter. For example, most brushes are made of graphite. Contact between the brushes and the commutator is required to complete the electromagnetic circuit and thus essential for motor operation in a brushed motor environment. As the brushes contact the commutator, wear occurs and very fine graphite particles, dust, in fact, escape into the air and also build up on the commutator at the contact area between the commutator and the brushes. When enough such particulates build up on the commutator, the brushes will fail to complete the electromagnetic circuit and the motor will no longer operate.

Clearly no motor lasts forever. However, in the case of brushed electromagnetic motors it would approach optimum if the motor life could be extended at least as long as the brush life. In practice, it has been found that typically first, the copper wire fails cutting motor life as the result of excess heat. And, subsequently, should the user be able to get by copper wire failure, dust or particulate build up, especially from graphite dust, similarly causes catastrophic and permanent failure.

As stated above, there is a long established need to cool electrical motors. This is especially true for brushed electrical motors, which are subject to long continuous and constant usage on a daily basis. In fact, a quick review of the US/PTO records shows that there are over a hundred references concerned with the cooling of electrical motors.

Most of the references found in the US/PTO are for liquid cooled devices.

Typically, these devices are non-brushed motors such as induction motors. Non brushed motors are also known as brushless motors. Brushless motors do not require a brush nor do they require physical contact of the brush with the commutator in order to make electrical contact and cause the motor to operate. Brushless motors use a dielectric fluid as cooling media.

With respect to the brushed motors references, typically air is used the as cooling media. Typically, the brushed motor references related to cooling focus on improving cooling by integrating a heat sink on the motor housing. In virtually all cases disclosed, an axial fan is used to cool and is integrated as part of the motor or separately connected. Such an axial fan draws air and pushes air towards the motor housing and attempts to provide cooling. However, whether integrated or separated from the motor, an axial fan provides high air flow but low air pressure.

U.S. Pat. No. 7,042,121 discloses an electrical motor having a cooling air flow generated by a fan wheel and routed through ventilation openings of the motor housing. The motor further includes a heat sink and a fan to aide in additional cooling,

For example, U.S. Pat. No. 4,092,556 discloses a closed system for cooling an electric motor that includes a rotor, a stator and a commutator. The motor includes ducts, which have openings opposite the surface of contact of the brushes and the commutator. Air is forced through the ducts from either side of the rotor on the contact. The fan from the air is directed through a cooling path by cooling elements and designed to increase cooling flow and add effective cooling to the motor. The cooling elements are external to the motor.

Thus what is needed is a motor, which lasts as long as the brushes, while being able to provide high speed operation in a confined environment. As explained below, the instant invention provides an apparatus and method, which provides adequate cooling to extend motor life through preservation of the cooper windings and by clearing the contact area of graphite build up.

SUMMARY

OF THE INVENTION

A method and structure for cooling a small high powered electrical motor, which includes the motor in accordance with the invention having cooling structure. The cooling structure provides forced and pressurized air at the area of contact between the brushes and the commutator. The air hits the commutator contact area with enough force to cool the copper wires and dislodge particulates, notably graphite particles from the contact area.

It is an object of this invention to provide a method and structure for cooling a small high powered electrical motor.

It is an additional object of this invention to provide such a method and structure for cooling a small high powered electrical motor, which dislodges graphite particles from the contact area between the brushes and commutator to extend the life of the brushes.

It is an additional object of this invention to provide a method and structure for cooling a small high powered electrical motor, which extends the life of the motor by extending the life of the brushes.

The motor in accordance with this invention employs a centrifugal fan to compress and blow air towards the commutator. In one exemplary embodiment, the fan comprises an impeller. The impeller forces the air flow towards the armature and in particular toward the contact area. Forced air cools as it passes through motor housing and along the heat generating components. Particularly, the forced and pressurized air flows past the heat generating components including the brush, the commutator, and copper windings as well as the armature causing cooling as it goes.

Additionally, the air flow is of sufficient strength and pressure to dislodge particulates. Particularly, the brushes of such motors are made of graphite. Small bits of graphite defining dust particles cause build up on the contact area. By providing such a flow of air that dislodges particulates, including graphite dust from the contact area, particulate build up at the contact area is discouraged, if not eliminated. Additionally, it will be appreciated that a commutator having a dirty contact area will lower the motor efficiency. Further, such a dirty contact area will likely generate extra heat due to a partial shorting of the circuit between the commutator and the brushes.

In accordance with one exemplary embodiment of the motor of the invention, which comprises: an electric motor having a motor housing, a stator, a rotor having a commutator and brushes for contacting the commutator at the contact area; a forced air cooling assembly including: a fan for creating air flow; a manifold for accelerating the air flow; the manifold have exit ports and the exit ports being positioned directly over the contact area for directing the accelerated air flow at the contact area; and the motor housing having a plurality of opening; at least one opening aligned with the contact area and at least a second opening defining an exit vent.

In another exemplary embodiment, the electrical motor in accordance with the invention includes a manifold having two impeller exit ports which are opposed from one another and having contact area intakes and they, too, are opposed from one another.

It is an advantage of this invention to provide such an electrical motor, which increases motor life in a confined environment.

BRIEF DESCRIPTION OF THE DRAWING

For a further understanding of the objects and advantages of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawing, in which like parts are given like reference numerals and wherein:

FIG. 1 is a partially cut away perspective view of the electrical motor in accordance with this invention.

FIG. 2 is a partially exploded view of the electrical motor in accordance with this invention showing detail of one exemplary manifold.

FIG. 3 is an enlarged cross sectional view of the reverse side of the manifold of the electrical motor in accordance with this invention.

FIG. 4 illustrates the air flow from the impeller to the exit vents in the motor housing in accordance with electrical motor of this invention.

FIG. 5 illustrates the electrical motor of this invention in use.

DETAILED DESCRIPTION

OF THE INVENTION

An exemplary embodiment of the electric motor in accordance with the present invention generally denoted by the numeral 20 will now be described with reference to FIG. 1. The motor 20 includes a stator 22 or housing, an armature 24 or rotor and a brush assembly, generally denoted by the numeral 26.

The armature 24 includes a commutator 28. Typically, the commutator 28 uses copper segments. However, more modern examples of the commutator 28 include graphite segments.

The brush assembly 26 includes a brush holder 30 for holding a brush 32 against the commutator 28. The area which the brush 32 contacts the commutator 28 is called the contact area.



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stats Patent Info
Application #
US 20140042867 A1
Publish Date
02/13/2014
Document #
13862040
File Date
04/12/2013
USPTO Class
310227
Other USPTO Classes
International Class
/
Drawings
6


Brushes
Centrifugal Fan
High Speed
Motor Housing


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