Fluid reaction surfaces (i.e. – impellers) – Articulated – resiliently mounted or self-shifting impeller...
Reexamination Certificate
1999-07-01
2001-03-13
Ryznic, John E. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Articulated, resiliently mounted or self-shifting impeller...
C416S16900R, C416S24100B
Reexamination Certificate
active
06200098
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to controlling the rotational speed of an axial fan with particular application to a cooling fan of the type used in automotive vehicles to move air through a heat exchanger.
2. Description of the Prior Art
A ring fan is typical of cooling fans used in automotive environments. A ring fan includes radially extending blades which are connected at the distal ends by a ring. The ring provides added stability and rigidity to the blades and improves noise performance of the fan. The fan noise is a serious problem in automobiles, especially light trucks and sport utility vehicles.
Despite the advantages of noise reduction and cooling performance of ring fans, they have not enjoyed widespread use because the burst speed of a ring fan is generally lower than the burst speed of conventional axil fans, the burst speed being that speed at which the fan will break apart, i.e., burst, in response to centrifugal forces generated by the rotation. Naturally, automobile manufacturers use fans with very high burst speeds. Because the ring adds mass to the outside diameter of the fan, which increases centrifugal forces proportionally to the radius squared, engine driven ring fans have not met the burst speed requirements of automotive manufacturers.
SUMMARY OF THE INVENTION AND ADVANTAGES
The invention provides a unique method of driving a plurality of fan blades disposed about and engaging a driving hub at an interface by rotating the fan blades in unison with the hub up to a predetermined rotational speed and rotating the fan blades at a slower rotational speed than the hub in response to the hub rotating at a higher rotational speed than the predetermined rotational speed to prevent the fan blades from bursting in response to centrifugal force.
The invention may be implemented in a fan assembly comprising a hub adapted for driving connection to a rotary drive and a plurality of fan blades extending radially from the hub. The fan blades consist of a first composition and the hub consists of a second composition different from the first composition. The assembly is characterized by a driving connection between the fan blades and the hub for rotating the blades in unison with the hub up to a predetermined rotational speed and for allowing rotation of the hub independently of and at a higher speed than the fan blades in response to the hub rotating at a higher rotational speed than the predetermined rotational speed to prevent the fan blades from bursting in response to centrifugal force.
Accordingly, the subject invention may be utilized in a ring fan to prevent the fan from ever reaching burst speed whereby ring fans, with all of their advantages, may be used more extensively without fear of breaking apart.
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Kennedy Larry C.
Moser George
BEHR America, Inc.
Howard & Howard
Ryznic John E.
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