Vacuums!

[ngreen]

Reversing the compressor is a bad idea. Especially when we have a venturi vacuum generator that works perfectly fine with compressed air. Plus the advantages of using the compressor are that multiple functions can be powered by the compressed air it generates.

There are other, non-pneumatic, ways of producing a vacuum. Driving a piston with a motor works, but relies on a good seal (you can only evacuate the length of the piston). Drawing a good seal is still important for continous vacuum device, such as the venturi or a KOP motor+impeller, but since these type are always drawing in air, loss of seal doesn't mean loss of object.

One other disadvantage (or advantage) of piston type suction devices are that once the seal is made, the amount of suction is determined by how far the piston rod moves. Since continous type are open to atmospheric pressure the vacuum is determined by other things like air flow rate and pressure or motor speed.

If you are using pneumatics this year, the venturi pump is great. If you not going with a pnuematics a KOP motor with an impeller (FP with an impeller from a small shop vaccum worked great in '04) will work and can fairly small and light (you only near the small motor, impeller (plastic), and a housing).

[Peter Matteson]

Originally Posted by ngreen

There are other, non-pneumatic, ways of producing a vacuum. Driving a piston with a motor works, but relies on a good seal (you can only evacuate the length of the piston).

Not true. Just be more creative and you'll figure it out.

[ngreen]

Originally Posted by Peter Matteson

Not true. Just be more creative and you'll figure it out.

I can think of being able to evacuate with a partial throw and continue to slightly move the piston as one way.

Another way is when the end of the stroke is reached, switch the vacuum side of the piston to atmospheric pressure (solenoid with other outlet blocked) and move piston to starting position, swithc to open to the suction device again and then continue to evacuate.

Or the third is to run two connected pistons driven by a crank shaft with switching between the two vacuum chambers via solenoid.

The third is the most complex and closest to a continous vacuum. The second you have to stop for a bit to move and the first you still are stuck at the end of the throw.

edit: actually a single piston would work for the third. Just use a solenoid to switch because either way you pull/push the piston you will get a vacuum. Still this isn't continous because of the stops at the ends of motion. Also without care the switching may introduce enough atmospheric air to break the seal.