Wednesday, 06 July 2011 14:26
as published in Product Design & Development, February 11, 2011
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.
The vacuum not only holds the leg on, but it also makes the prosthetic feel lighter and stabilizes the bind between the limb and prosthesis.
“Normally, as amputees will tell you, when they put the leg on in the morning it will usually fit fine, but it shrinks and continues to shrink all day as a result of the positive pressure of the prosthesis,” says McKinney. “But with elevated vacuum, if it’s higher than 15 in-Hg, which these pumps are, it keeps the limbs from shrinking.”
According to McKinney, limbs normally shrink anywhere from seven to 12 percent of their limb volume in the course of the day. In vacuum, they shrink less than one percent, and problems typically don’t occur until four percent. The seal between the socket and the limb and liner is not perfect. Over the course of several hours, the vacuum will diminish and the pump has to be able to reestablish the vacuum.
The pump was Fleming’s brainchild and was designed specifically for this application.
“What’s unique about the pump itself is the fact that it’s very small, but it’s capable of generating a relatively high vacuum level [up to 25 in-Hg] and that compares to an absolute vacuum level of about 29 in-Hg,” says Fleming. “In most actual installations, nowhere near 25 in-Hg is required. They typically run up to a maximum of about 20 in-Hg.”
The Devil is in the Details continue...
Wednesday, 10 November 2010 14:29
as published in Machine Design - October 21, 2010
The 2102x Series diaphragm pump is said to provide the highest vacuum levels from a pump of its size. The pump, which measures just over ½ in. in thickness and weighs less than 1 oz., has been upgraded to reliably achieving 27-in. HG and 30 psi.
Friday, 02 April 2010 00:00
as published in Machine Design - March 2010
After seeing a need in the medical equipment industry for smaller, lighter, and more efficient vacuum pumps and compressors, Dynaflo was incorporated in 1998, and entered the market with an innovative line of super-compact and lightweight products. Over the years, Dynaflo has shipped thousands of vacuum pumps and compressors to both domestic and international customers for a variety of medical and industrial applications, and has built a reputation for producing customized solutions to engineering design challenges. Today, Dynaflo’s cuttingedge designs continue to be at the forefront of custom pump and compressor engineering.
A New Dynaflo Radial Compressor Uses A Dozen Diaphragms Pumps continue...
Monday, 01 March 2010 00:00
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.
Dynaflo Radial Diaphragm Air Compressor continue...