Quote:
Originally Posted by Don Rotolo
If you use the vacuum, you can turn it off with a solenoid valve when you don't need it (also, how will you release the tube without a valve??). Vacuum off means no air consumption, right?
On a related note: In 2005 when we used pneumatics, the compressor essentially ran 100% of the match, so count on that. Note that even with 4 small CIMs, a compressor, and more, the batteries have the power.
Don
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(Vacuum off means no air consumption, right?) Correct. You turn it off with a valve connected to the
pressure input port of the vacuum generator. The generator's output is connected directly to the cup.
(How do you release the tube?)
(1) Just turn off the pressure input! The vacuum is generated by the Venturi Effect. Think about when you blow across the top of a straw that is in a drink cup. A vacuum is generated in the straw's column from the rapidly moving airflow across its top opening. But what happens? The fluid rises
ONLY as long as you are blowing. When you cut off the pressure, air zips back in along the tube, and the column of fluid drops like a rock. Similarly, without suction, the vacuum in the green tubing bleeds out rapidly (from the generator end). No vacuum, no holding force. Then, the Ringer's weight (or your robot pulling back) separates the cup from the Ringer.
(2) In industry, for faster action you add a "blow off" connection. This injects a bit of air to "eject the held object". That can easily be done here by adding a second valve to provide air in the link between the vacuum generator and the suction cup. BUT, if you keep the vacuum generator to suction cup line short, it probably will NOT be needed.
Now if you don't like the speed and DO decide to add a blow-off connection, be sure to keep the pressure as low as you can that still allows the (piloted) valve to reliably operate. That'll probably be in the 20-35PSI range. After all, you don't need much air at all, just a tiny puff! You may also wish to consider adding a flow regulator to the valve's output, just to reduce the airflow further. BUT REMEMBER, if you quickly change your mind about gripping and try to grab again right away, it MAY take a fraction of a second longer to grab. (After all, you may have to purge the additional blow-off air you just injected.)
BTW... Don't forget to plug the other (normally closed) output side of the blow-off valve!
(Failure to do this should become obvious pretty quickly, when all your compressed air escapes... Hee Hee...)
Now I seriously doubt that you'll
need a blow-off connection for this application. That's one of the main reasons FIRST provided such a tiny connection tubing for the suction cup. The total volume of air it takes to refill the vacuum line is VERY small. The instant you turn off the air supply to the generator, room air should rush back in along the green line (from the generator's end) in a flash.
Does this answer your question?
- Keith