You Can Compress Air; More Power Through More Pressure; The Check Valve - fischertechnik Profi Pneumatic II Manual De Instrucciones

2.2 You can compress air

Experiment:
Once again, take the cylinder with the blue piston rod, and pull
this completely out. Keep Connection A closed, and try to push
the piston rod through. What did you observe?
Observation:
The piston rod is only able to be pushed in a short distance. If you
let go, it springs back.
Answer:
The air in the cylinder is able to be compressed. The more it is
pressed together, the larger the pressure in the cylinder is. You can
also measure and calculate this pressure. The unit for pressure is
called "bar" or "Pascal".
The formula for calculating the amount of pressure is:
Force
Pressure = or, in short:
Area
Therefore, the amount of pressure depends on how much force we
exert on the round area in the inside of the cylinder.

2.3 More power through more pressure

Next, we want to determine which forces we are able to exert with
our cylinder. For this purpose you will construct a small lifting platform —
as is described in the Construction Manual starting on page 5.
Now we will conduct a few experiments with this model:
Lifting Platform Experiment 1 (see Construction Manual p. 5):
First of all, try to move the lifting platform upward by breathing air
into the cylinders through a tube. Despite maximum effort this will
not function.
Connection A
F
p =
A
Lifting Platform Experiment 2 (see Construction Manual p. 7):
Now, utilize a second cylinder with blue piston rod, attach it to the
building board next to the lifting platform; extract the piston rod
completely, and connect the tube to Connection A, which leads to
the lifting platform's cylinder.
Push the piston rod through. What happens? — The lifting platform
moves upward. Pull the piston rod out again, and you will see that
the lifting platform moves downward again. So far so good.
But what happens, for instance, if you place a book on the lifting
platform, and then try to lift it upward?
First, you have to compress the air in the cylinder quite a bit before
the book moves upward. In addition, the lifting platform is no longer
able to be completely extracted. How does that come about?
More force is required in order to lift the heavy book upward. You
can only obtain this force by increasing the pressure in the lifting
platform's cylinder. The compressed air requires less space in the
cylinder. Thus said, there is no longer enough "compressed air"
available in the cylinder in order to completely extend the lifting
platform. We must be able to pump more compressed air into the
cylinder.
And for this purpose we will utilize the so-called check valve.

2.4 The check valve

Now, if you extract the
piston rod from the
cylinder, the check
valve sucks outside air
into the cylinder.
If you push the piston
rod further inward, the
air is pumped out into
the tube through the
second opening in the
check valve, while the
firstconnection remains
closed. Now we have
constructed an air pump
similar to that which you
have on your bicycle.
The check valve is simply attached to
Connection A on the cylinder. The tube
can be connected to the check valve.
Tubing connection
Suction
GB+USA
Blow-out
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