Resources:
See a drawing of the device’s cross sections and output waveform
See a drawing of the device’s pressure plot

The Ultraflush nasal irrigator from inventor Mark Carpenter comes in the form of an inexpensive squeeze bottle that lets users rinse their nasal cavities by generating continuous flows or pulsating streams of saline solution in large quantities (150 to 600 cc). The device targets sufferers of nasal allergies and sinus infections as well as postsurgical patients.

Carpenter says saline nasal irrigation has grown tremendously, with annual sales doubling in each of the last three years. Pharmacies carry a selection of these devices. There are Neti pots or simple teapot-shaped devices to pour the solution into a nostril; simple squeeze bottle irrigators; and motorized piston-pump irrigators that produce a pulsating stream of saline solution. The pulsating stream is the most effective at cleansing the nostrils, but the devices are costly and complicated. Thus, squeeze-bottle irrigators dominate the market.

Current squeeze bottle designs have a convoluted flow path that demands an impractically large squeeze effort. Or they require a large number of components.

In contrast, Carpenter’s idea has only four parts: a squeeze bottle, cap, rigid tube, and elastomeric tube. Any squeeze bottle can generate a continuous stream in a wide range of flow rates as the user adjusts squeeze pressure. The Ultraflush is different in that the geometry and material properties of the elastomeric tube, as well as the rest of the fluid passage, were specially engineered. Besides getting a continuous stream, users can also adjust the pulsating stream to hit amplitudes up to three times higher than those of the best currently available pulsating irrigators.

For a continuous flow, a light squeeze of the bottle generates a relatively low internal pressure that drives the fluid into the elastomeric tube, then through the rigid tube and cap to the nostril.

For a periodic pulsating flow, users apply a hard squeeze. This makes the saline solution flow through the pickup tube at an accelerated flow rate. As the flow rate rises, it generates more differential pressure across the elastomeric tube. The pressure inside the tube is reduced relative to the pressure acting on the tube exterior due to Bernoulli’s law.

Once the flow rate through the tube reaches a critical level, the pressure differential makes the tube buckle (to a pinched flat configuration) and the fluid flow stops nearly instantaneously. Pressures outside the tube then equalize, elastomeric forces return the tube to its fully open position, and the cycle repeats.

The pressure gradient along the length of the tube assembly makes the position of the buckling closure predictable and consistent. Also, since the liquid accelerates over a relatively long portion of the cycle while the buckling happens rapidly, the flow versus time function is in the form of a saw-tooth wave. Carpenter believes this action provides a more-beneficial stream than does the rectified sine wave produced by piston-pump-based irrigators. The frequency of pulsation is nearly constant and is “tunable” merely by varying the length of the entire tube assembly. The Ultraflush’s frequency is tuned to 20 Hz.

Carpenter has patented the Ultraflush (#7,976,529) and has fabricated 200 prototypes. He is currently looking for interested licensees, investors, and partners. He also believes that the principle involved in using a flow-generated pressure drop to collapse a tube and create a periodic fluid flow, which he has trademarked as PurPulsator Technology, will find application in other devices and industries. Perhaps Machine Design readers can suggest alternate applications? He can be reached at Skylab Developments Inc., (313) 477-2829, mark@skylabdev.com.

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