as published in Product Design & Development Jan/Feb 2011
by David Mantey, Editor, PD&D

With a growing amputee population, two firms partner to design artificial limbs that use vacuum pumps to increase circulation, comfort, and quality of life.

Until recently, artificial limbs were held on via archaic methods, such as straps, sleeves, or pins. All of the former methods allowed for certain types of motion, motion that creates sores and pressure. Ray McKinney, certified prosthetist orthotist (CPO) of McKinney Prosthetics, and his partner in design, William Fleming, president of Dynaflo, have developed a vacuum suspension system to create a seal that securely holds the prosthesis to the limb.

The new system eliminates excess motion and, since the vacuum pressure is high enough, it converts perspiration from the socket to a vapor that seeps out through the pump back into the atmosphere curing another ailment of the below-knee amputee community.

as published in Machine Design April 16th 2010

radial internals2

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, but flow pulsation, noise, vibration, low speed cogging and limited dynamic range are common problems for typical reciprocating designs that rely on one to four diaphragms.


12 diaphragms

Dynaflo, Inc. has introduced a new radial compressor aimed squarely at these shortcomings. Flow pulsation and noise are minimized by means of a significantly larger number (12 in the present example) of relatively small pumping diaphragms, and for this device, Dynaflo has developed a highly compact design, utilizing rectangular-shaped diaphragms disposed in a uni-planar, radial array and actuated by a common, eccentrically driven, central drive element. This arrangement allows for near perfect primary balance, resulting in virtually zero mechanical vibration, and 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.