induce vibration into a short (12") length of medical hose (0.125 OD)

[brian15co]

Hello,

I am looking to induce vibration into a short length of .125 in. OD medical hose. The goal is to lightly "shake" the cellular suspension slowly moving through the hose in a hope to eliminate de-homogenizing of this suspension.

What makes a cell phone vibrate? I am looking for something similar, maybe with a smaller amplitude of vibration. I have been pointed towards piezo films, although I am unfamiliar with these. I have attached a visual.


Brian L
Colorado School of Mines

 

[btrueblood]

Cell phones vibrate by having a motor spin an unbalanced rotor. Typical frequencies are in the 10's of Hz.

Piezo films will want to vibrate (have natural frequencies) in the 10000's of Hz. Ultrasonic frequencies have, I believe, some known degradative effects on biological specimens.

Electric solenoids, or "voice coil", actuators can respond in frequencies somewhere between the above two, you can tune them to some extent by adding/subracting mass from the driven element.

 

[Strong]

Brian,

I suppose the trick is to find the best frequency and amplitude of the vibration that works. You can glue the tube directly to one or more speaker elements or indirectly connect using a "stinger" (light weight rod). A function generator, or PC with tone generator, and a power amplifier would be all you need. A tiny accelerometer could be used to measure the vibration levels and provide feedback to a control system. There are more elegant ways to do this, but you need to isolate the vibration parameters that work and then optimize the setup. Hint: you may also want to excite vibratoin in the axial (inline) direction and not just the radial direction.

Walt

 

[Tmoose]

I'd expect a variable speed motor on an axially or radially flexible platform at one end on could be adjusted to make any shape I liked.

http://www.uq.edu.au/_School_Science_Lessons/26.3.0.GIF

Speaking of radial phenomenon, yesterday an SKF application engineer told me that radial clearance and diametral clearance are the same thing. Well.............

 

[Strong]

Following on with Tmoose standing wave pictures, I suspect that there would be no motion of the material inside the flexible tube. That's why I suggested axial excitation; the same principle that is used in vibratory bowl feeders. The vibratory motion is in the direction of motion!

Walt

 

[gt6racer2]

Hi,
Assuming that the fluid is supplied to the hose by a pump, then a more effective and easier solution might be to run a return line from the output end so that the fluid is always recirculating back to the source. Restricting flow in the return line ( with a valve packaged near the source ) would cause pressure increase (flow) at the output end. By making the pump and hose "loop" flow capacity larger than the highest demand, you'll always have some recirculation, even at highest demand. ( The output would of course need a spring loaded valve to prevent flow due to the return line pressure drop ).