ENGINEERING INSIGHT
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Valve supplier Smart Products played a key role in helping Energy Prosthetics develop an autoexpulsion valve for prosthetic devices. The technology recently was purchased by Otto Bock Healthcare GmbH.
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Prosthetic limbs typically are fitted with a valve that expels residual air from the socket and creates suction to hold the device in place. When the wearer of the device sits down, a tiny amount of air can leak between the skin and the socket’s flexible liner. This can create discomfort when the patient stands, unless he or she is able to expel the air. This can be problematic because of the types of valves that have been traditionally used, notes Adam Soss, CEO of Energy Prosthetics (Winnetka, CA, USA). An amputee himself, Soss decided to do something about it.
“I know it’s difficult to picture if you don’t wear a prosthetic device, so let me explain it this way,” says Soss. “Imagine sliding your finger inside a long thimble with a tiny hole at the end. As your finger slides in, any air trapped inside would be expelled out of the hole. Once your finger is completely inserted into the thimble, and the hole is blocked off, the thimble cannot come off because of the suction. The valve on a prosthetic device represents the finger blocking this tiny hole.” Releasing the valve pressure allows the prosthetic to be removed.
Soss felt there was room for improvement in the valve design. “The main issue is that [the existing] valves are threaded into a base. This causes problems for geriatric patients with poor hand dexterity. And with many of the valves, patients must push a little button to actuate them. Manufacturers have tried using autoexpulsion valves, but they have a tendency to leak or clog.”
After brainstorming with engineer and high-school friend Dustin Bouch, Soss conceived of a “push-in” valve, meaning it would not have to be threaded, for a new prosthetic device. The valve would act like an autoexpulsion valve without the associated leaking and clogging problems, and it would not present the difficulties of threaded valves. Lacking the budget to develop a custom valve from scratch, Soss and his partners had to find an existing valve that they could modify for their application. Enter Smart Products (Morgan Hill, CA, USA).
From Partnership to Prototype
Soss found Smart Products the old-fashioned way: he Googled “check valves.” The company sent him samples within a week, but none of them were quite right for Soss’s prosthetic prototype.
In short order, a company technician found a shortened version of Smart’s110 check valve, a modified valve that had been made for an earlier project. The valve didn’t protrude outside the prosthetic device and its design was close to what Soss actually needed. In addition, the valve’s spring-loaded poppet pushes against the O-ring to produce a positive seal. Soss was also able to select the precise pressure he needed to create the necessary suction in his new prosthetic design thanks to Smart Products’ large availability of spring rates. Smart Products worked with Soss to determine spring pressures and customized O-ring materials for the valve, allowing Soss to fine-tune the valve as his prototype evolved.
Because of the length of time that had passed since the modified 110 check valve had been in production, the mould no longer existed, and Soss’s budget didn’t include engineering a new mould. In the end, Soss purchased the remainder of the stock and used the valves as he began to take his device to market.
According to Soss, his new device automatically expels air without leaking or clogging. He credits Smart Products for assisting in the development of the device. “The company has definitely been a true partner in the design process of my device and helped me get it to market faster,” says Soss.
German prosthetic device company Otto Bock Healthcare GmbH (Duderstadt, Germany) recently purchased the PushValve and MagValve rights from Energy Prosthetics. Smart Products will contract to manufacture the autoexplosion valve once the company begins incorporating it in prosthetic devices.
