worked for other builders and — more
importantly — what didn't work so well.
There are several ways to pump
liquids. For example, you can use a
simple gravity feed and a valve to
release the liquid from an inverted
bottle or container. There are many
types of electrical pumps that are
mostly designed for water or fuel.
There is a special type of pump
called a peristaltic pump (often used
for medical pumps) that squeezes
plastic tubing with a rotating cam. Or,
you can implement a pressurized
bottle and force the liquid from the
bottle by overcoming the atmospheric
pressure using a compressed gas or air.
After reviewing the designs and
costs involved, I decided to use a
pressurized system since I was familiar
with fuel injection arrangements in
gasoline or diesel engines. Basically, I
call my system pressure timed.
To keep the system food safe, I
had to find commonly available
containers, lines, and fittings that
would not react to concentrated Ethyl
alcohol or the acidic nature of many
of the fruit juices or other mixes. This
led me to using two liter polyethylene
I figured this would be easy. I was
wrong. The hardest part of this
project was finding a way to attach
fittings to a two liter bottle and
keeping it from leaking gas.
I tried rubber stoppers, corks held
on with tie-wraps, hose clamps, and
even tape. I became quite frustrated.
Then, I found a home brewed beer
dispenser project on the Internet that
used the original bottle cap and a
modified 3/8 inch brass compression
fitting, a 1/2 inch brass washer, two
1/4 inch brass barbed fittings, a
copper dip tube, a rubber washer,
plus a 1/4 inch T fitting.
For the original pressure testing, I
used an oilless air compressor and a
Post comments on this article at www.servomagazine.com/index.php/magazine/article/february2014_Nelson.
SERVO 02.2014 45