One long accepted yet problematic solution in fluid controls has been the steel clamp. A water quality instrument manufacturer and a bass boat manufacturer have both found user-friendly alternatives to this traditional fix.
Needle pinch valves
HF Scientific has been in business for decades producing instrumentation, test kits, and chemical reagents used for monitoring water quality in a variety of applications. One of its water quality testing products, the MicroTOL Online Turbidimeter, measures the amount of particles suspended in a liquid (turbidity). This is done by measuring the scattered and transmitted light through the liquid -- usually water.
A Flow-Rite needle pinch valve is used on HF Scientific’s MicroTOL Online Turbidimeter.
For the instrument to give an accurate reading, bubbles cannot be present in the liquid for the instrument to misread as particles. A stainless-steel medical clamp was originally added to one of the tubes to control back pressure, thereby keeping air in the solution and avoiding a reading error. This clamp was unattractive and often fell off. Functional complications arose when it was exposed to sunlight.
Without an alternative available, the company used this clamp for about 20 years. That is until Michael Goodman, director of technical services at HF Scientific, discovered needle pinch valves by Flow-Rite while reading a trade magazine.
As Goodman researched, he learned the valves fit the requirements for the turbidimeter to control back pressure. The valves do not require fittings, cutting, or removal of soft wall tubing. There is no fluid contact with the valve, since it remains on the outside of the tube. It is designed for fine adjustment of fluid flow, and the valve has a range of zero to full flow. The 1mm divided metered scale on the valve body enables calibration to be recorded and replicated -- a feature not possible with the original clamp. The valves are easily installed by sliding the bottom half on the tube and metering with the top.
The decision was then made to implement the needle pinch valves, and HF Scientific has been pleased with the results ever since. "Air is no longer an issue for the turbidimeter," Goodman told us. "UV exposure doesn't affect the valve, nor has there been a single problem with its function. They aren't thrown away or fall off anymore, since they can just be loosened or tightened but still remain on the tube. It"s also more aesthetically pleasing compared to the steel clamp." As for being user-friendly, Goodman said: "The pinch valve is intuitive -- there was no need to train our customers. It's easier to use, and customers value calibration being repeatable."
Here is a link to the section of the Flow-Rite website that covers the Quik-Lok connectors. Pretty simple in operation and effective. Definitely following the KISS principle.
Warren, no joking about not having a full bookshelf anymore for research. I entered the field just before the web arrived, and remember getting data sheets the old fashion way. Want to learn about some new product? Oh, you need to look up the manufacture in the Thomas Register (aka "Big Green Books")....
And writing code, especially for Microsoft products? What was a time consuming and difficult process, is now complimented by being able to grab tons of examples off of the internet, along with the reference material right from Microsoft.
Let's see, I also remember using modems to dial into customer machines, sending FAXes to order stuff, etc.
Sometimes I miss being able to use the "I'm compiling right now" excuse.
And since I am a pack rat, I do still have one full set of brand new, still in the box, Texas Instrument logic books (the yellow ones with the blue stripe).... :)
I was particularly intrigued by the simple, yet very effective pinch valves. I was able to go to the site from the link in the author's sig line and learn even more.
Unfortunately, searching on that same site for more information on the Quik-Lok produced no results at all. While I believe that I have a fair idea of how this type of quick disconnect works, it would have been much more informative if the author's website provided that information.
I think it is great the communications we have now. I used to have a shelf FULL of transistor and IC books. Now I have the web and no books. I read Design News, Electronic Products, EDN, etc. and find all sorts of useful things.
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New versions of BASF's Ecovio line are both compostable and designed for either injection molding or thermoforming. These combinations are becoming more common for the single-use bioplastics used in food service and food packaging applications, but are still not widely available.
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