Plastic and nonmetallic article shaping or treating: processes – With measuring – testing – or inspecting
Utility Patent
1999-07-26
2001-01-02
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With measuring, testing, or inspecting
C249S155000, C249S158000, C264S328100, C425S19200R
Utility Patent
active
06168734
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a dynamically balanced centrifugal fan and a method for balancing such a fan. More particularly, the present invention relates to a dynamically balanced centrifugal fan having a fan inlet ring in which the radial thickness of ring is varied to correct imbalance of the fan.
2. Disclosure Information
Centrifugal fans can be utilized for a variety of applications where air movement is needed, such as the ventilation system in an automotive vehicle. Centrifugal fans are typically molded from a synthetic polymeric material to reduce weight, reduce manufacturing cost, and ease assembly into a system. Typically, molded plastic fans must be balanced during the manufacturing process and typically this is done through a selective distribution of plastic material within the mold used to manufacture the fan. Other post-molding balancing practices include the addition of weights to the fan, such as with clips.
Since plastic fans are usually manufactured by an injection molding process, the fans can be dynamically balanced during that process once the zone and magnitude of the imbalance is determined. Typical methods for balancing plastic fans in an injection molding process have involved machining away material from a predetermined location of the mold to increase the amount and increase the weight of plastic at these locations by allowing additional plastic to be added to obtain the desired balanced weight distribution. While this method has been proven to be acceptable, continued machining away of material and the mold ultimately destroys the mold forcing the fabrication of a new one.
Other attempts to dynamically balance fans during a molding process involve the use of screws located at fixed points within the mold. Once a fan has been determined to be imbalanced, the screws can be changed to allow more or less plastic material to flow into the threaded aperture of the screw to provide more or less weight at specific locations to change the balance of the fan. Typically, the screws are located at fixed locations in the mold such that the thickness of a portion of the fan is changing in a generally vertical plane in an axial direction relative to the rotational axis of the centrifugal fans. While this method has been proven to be useful, it involves a substantial amount of “trial and error” of moving a multiple number of threaded screws to achieve the balance needed for the fan.
Therefore, it would be desirable to provide a method for balancing a centrifugal fan which does not require machining away of the fan mold and which can be accomplished quickly and easily. It is an object of the present invention to provide a method for dynamically balancing a fan in a radial direction, not vertically in an axial direction.
SUMMARY OF THE INVENTION
The present invention overcomes the problems associated with prior art by providing a method for balancing a blower fan wheel of a blower fan assembly, the blower wheel having a central hub portion, a generally circular fan inlet ring having a generally uniform cross-section and a plurality of fan blades disposed between and supported by the hub portion and the fan inlet ring. The method comprises the steps of forming a first blower wheel in an injection molding process and measuring the first blower wheel to determine a zone or location and a magnitude of an imbalance thereof. The method includes adjusting the cross-section of the fan inlet ring in a radial direction at a predetermined location by a predetermined amount to provide an area of greater cross-section than the remainder of the fan inlet ring during the injection molding process. This area of greater cross-section in a radial direction of the fan inlet ring balances the fan blower wheel at the plane of its ring.
In one embodiment of the method of the present invention, a generally Z-shaped inlet ring is formed in the blower wheel, the Z-shaped inlet ring including a first vertical portion extending axially along an outer diameter of the fan blades, a generally horizontal portion disposed over the plurality of fan blades and a second generally vertical portion disposed radially inwardly from the first vertical portion and extending upwardly from the generally horizontal portion. The step of adjusting the cross-section of the fan inlet ring in the radial direction includes increasing the thickness of this second vertical portion of the Z-shaped inlet ring at a predetermined location by a predetermined amount of plastic to balance the blower wheel at the plane of the ring. In one embodiment, the radial thickness of the second vertical portion is increased to a limit which does not exceed the outer diameter of the blower wheel.
A centrifugal fan balanced by such a method is also disclosed by the present invention as well as a mold for forming such a fan. The mold includes a pair of mold halves for forming a central hub portion, a generally circular fan inlet ring and a plurality of fan blades extending between the hub and the fan inlet ring. The mold also includes a generally annular ring disposed in one of the mold halves for varying the radial thickness of the fan inlet ring, in a manner as described above.
It is an advantage of the present invention to dynamically balance a centrifugal fan blower wheel at the plane of its ring by increasing the radial thickness of the fan inlet ring. This protects the packaging of the centrifugal fan within the air moving system. Furthermore, it is an advantage that the fan can be dynamically balanced without damage to the mold used for fabricating the fan.
These and other advantages, features and objects of the invention will become apparent from the drawings, detail description and claims which follow.
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Heitbrink Jill L.
McCoy-Pfau Rhonda L.
Visteon Global Technologies Inc.
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