Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-10-14
2001-02-27
Tamai, Karl (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S062000, C417S356000
Reexamination Certificate
active
06194798
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Not Applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not Applicable
REFERENCE TO A “MOCROFICHE APPENDIX”
Not Applicable
BACKGROUND
This invention relates to fans and more particularly to DC motor driven fans with stator electromagnets displaced radially beyond the periphery of the rotor.
DESCRIPTION OF RELATED ART
This type of fan is known, for example, by U.S. Pat. Nos. 4,553,075 and 4,459,087. The '075 patent includes an annular permanent magnet magnetized in segments about its circumference. Each segment is oppositely radially magnetized with respect to its adjacent segments. Fan blades are located within the annular magnet. A coil comprising two electrically independent bifilar wound windings, connected to be oppositely energized, and an electromagnet structure defining two pole pieces reside outside the permanent magnet annulus. A Hall effect device alternately energizes the separate coil windings in response to passage of the segments of the rotor magnet to alternately produce opposite magnetic fields in the pole pieces.
The '087 patent includes a fan unit for cooling an internal combustion engine comprising a fan impeller associated with a coaxial channel for guiding the air traveling through said impeller and an electric driving motor of DC type. The channel is fixed to the ends of the blades of the impeller and rotates with the impeller and itself constitutes the rotor of the electric motor whose stator coaxially surrounds at least a part of the channel. The stator is rigid with a fixed shaft around which the impeller rotates.
The fan units disclosed in both of these prior patents and, indeed, in the known prior art suffer from the disadvantage of requiring large mass ring member that encircles the distill edges of the blades in order to establish the N-S radially oriented magnetic segments that cooperate with the stator electromagnetic fields to generate torque and motion. These members prevent miniaturization of the fan design, require a large mass ring member or expensive magnetic materials which increases manufacturing cost and power consumption during operation and generally lowers the efficiency of the fan unit.
BRIEF SUMMARY OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION
An exemplary embodiment according to the principles of the present invention includes a DC driven fan with blades made of magnetized material and substantially permanently magnetized in the radial direction. In this way, the structure of an annular large mass magnetic ring, as found in the prior art, can be eliminated or reduced because, according to the principles of the present invention, its function has been transferred to the fan blades themselves. Alternatively, the mass of a magnetic ring can be reduced significantly because the mass of the blades contributes to the magnetic function of the impeller. The efficiency of the fan is enhanced by (i) making the outer edge of each blade wider than its inner edge, which tends to alleviate the contradiction between the two blade functions (1) to move air and (2) to produce torque, and (ii) eliminating or reducing the large mass (i.e., annular magnetic ring) from or at the outer edges or periphery of the blades.
In one exemplary embodiment, adjacent blades are magnetized in the opposite manner such that the outer-inner portions would comprise a N-S permanent magnet orientation and the adjacent blade outer-inner portions would comprise a S-N permanent magnet orientation. Each blade inner side is mounted in a non-ferrous hub.
Another feature of the fan according to the present invention enables the impeller to be formed by two sub-impellers with equal number of blades. All blades of one sub-impeller are magnetized uniformly, such as all outer portions being N. All blades of the other sub-assembly are magnetized uniformly, but opposite the first sub-impeller, i.e., all outer blade portions being S. The two sub-impellers are then fixed to each other and mounted about the same rotating axis with the blades of one equally annularly spaced from or between the blades of the other to form blade portions with alternating N-S orientations.
An alternate exemplary embodiment according to the principles of the present invention includes mounting each blade in a ferrous material hub to magnetically join the inner radial ends of adjacent pairs of magnetized blades. Accordingly, each adjacent pair of blades and associated hub portion function like a U-shaped or V-shaped magnet with its N-S field in the air-gap generated by the magnetized blades interacting with the DC pulsed-induced field of the electromagnet to power the fan.
Various important advantages result from a fan design according to the principles of the present invention, such as reduction in manufacturing costs, increased impeller airflow area, increased airflow per unit power consumed, reduced losses, enhanced miniaturization of fan dimensions while achieving low power consumption and high airflow specifications. This last benefit is important for small fans used, for example, in electronic equipment such as personal computers, fan trays, and a vast variety of electronic instrumentation apparatus.
The physical design of the fan system and shape of the blades can take a wide variety of forms related to predetermined applications. For example, principles of the present invention can be applied to axial flow fans, centrifugal flow fans, large, small and micro-fans, as desired.
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Air Concepts, Inc.
Dreyfus Edward
Tamai Karl
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