Using "balanced poppet," an ultra-sensitive pneumatic valve, has enabled engineers to build a device that could save lives of victims of smoke inhalation and carbon monoxide poisoning.
Known as a rebreather, the device allows emergency medical technicians to flush carbon monoxide and other poisonous gases from the lungs of victims. Powered purely by compressed air, the non-electrical device is targeted at fire departments, ambulances, and medical clinics.
The key to the development of the rebreather is a pneumatic poppet valve, custom-designed for the application by engineers at Humphrey Products Co. (www.humphrey-products.com). Humphrey engineers say that the poppet was key to the creation of the rebreather because it enables the ultra-sensitive operation that the valve needs in order to shift at critical moments.
"The valve's sensitivity ensures that the patient is not going to receive an inadequate mixture of gases," says Rich McDonnell, director of business development at Humphrey Products. "It prevents the rebreather from damaging the victim's respiratory system."
The valve accomplishes that by employing a so-called "balanced poppet." During operation, the poppet reacts to pressure changes from upstream gas sources, which feed oxygen and carbon dioxide gases into a valve manifold in the laptop-sized rebreather. By employing an offsetting spring and armature, the poppet creates a balanced situation, enabling it to quickly react to minute changes in pressure. As such, when pressure from the supply tanks exceeds a prescribed control window, the valve shifts from normally open to normally closed, preventing a victim from receiving the wrong concentration of gases. The valve, however, maintains a normally open status as long as the pressure from the blender remains within a ±3 psi window, or "deadband."
Engineers from Humphrey said that the initial inability to find a poppet sensitive enough to operate within such a small deadband almost prevented completion of the project. Similar poppet valves, McDonnell says, have deadbands of approximately ±20 psi, which would have exceeded the OEM's specifications for the product. (Humphrey engineers say they are as yet unable to divulge the name of the respiratory equipment manufacturer that makes the rebreather).
Because OEM engineers could not find an off-the-shelf valve to meet their needs, early iterations of the rebreather failed to work on a repeatable basis. Engineers redesigned the rebreather on several occasions, only to find that it would function within its prescribed specs for a short time before ultimately wandering outside the correct pressure ranges.
"They were almost ready to shelve the rebreather," McDonnell recalls. "They found that they just couldn't tune a valve to respond within the deadband they wanted."
Seeing the dilemma and knowing that no available commercial products could solve the problem, Humphrey engineers custom-designed the valve around the company's direct-acting 310 Valve. The new product now operates within the ±3 psi deadband in the low pressure rebreather application.
"In essence, when the valve senses a pressure differential, it shifts," McDonnell says. "So if there's any kind of failure or unusual interruption, the rebreather can react quickly."
As the rebreather project progressed, Humphrey engineers also worked with the OEM to consolidate the unit's valve assembly and manifold. To downsize the device, Humphrey eliminated all external connections, integrating them into the inside of a single manifold.
Lifesaver: Humphrey's custom-designed valve assembly
provided the sensitivity to build a laptop-sized unit capable of flushing
toxic gases from the lungs.
"We brought it down from the size of an ice chest to the size of a laptop
computer," McDonnell explains.
Humphrey engineers believe that the poppet valve technology may be applicable in other medical applications, as well. In hospital surgical suites, they say, it could one day play an as-yet-unnamed role of "tremendous potential."