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Compressor Airs Out Pump Shortcomings

Wed, 05/11/2011 - 10:37am
Bill Fleming

While diaphragm-type vacuum pumps can offer advantages for medical device manufacturers, they can also present several challenges for specific applications. This Tech Brief highlights a radial compressor that addresses these concerns.

Diaphragm-type vacuum pumps and air compressors have the advantages of a fluid path that may be completely sealed from the environment, and the potential for high efficiency and long life due to a lack of sliding seals. Flow pulsation, noise, vibration, low speed cogging, and limited dynamic range, however, are common problems for reciprocating designs that typically rely on one to four diaphragms.

Dynaflo's radial compressor design is aimed squarely at these shortcomings. Flow pulsation and noise are minimized by means of a compact, radial array of 12 relatively small, rectagular pumping diaphragms. Utilizing a common, eccentrically actuated, central drive element, this uni-planar arrangement allows for near perfect primary balance, resulting in virtually zero mechanical vibration. Due to the equal angular separation of each segment, the motor shaft is presented with minimal variation in torque load with respect to its angular position. This relatively constant loading allows the motor to be operated over a broader range of rotational speeds, resulting in a greater dynamic range for the overall device.

A unique feature of the drive mechanism is its fully symmetric architecture. Unlike the master-and-articulated-rod assembly found in a typical radial piston engine, each of the 12 driven segments in the Dynaflo design is identical, thereby insuring that the components of each segment are no more stressed than those of its neighbor. Another unique feature of the drive mechanism is the rolling pin coupling between each segment of the central drive and its driven diaphragm assembly. While allowing for the necessary lateral displacement of each drive segment with respect to its driven diaphragm, these roll pins provide an essentially rigid connection in the radial direction (also the direction of rectilinear motion), ensuring consistent positional control of segment components over a broad range of operating speed.

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Bill Fleming is president of Dynaflo Inc., a design and manufacturing company specializing in custom-engineered sub-fractional horsepower vacuum pumps and compressors for portable medical applications. He can be reached at 877-244-4330 or wtf@dynaflopumps.com.

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