Bimba Spring Supershifter Piston

[rcmolloy]

So today we started making a universal test chassis for our programmers to implement on before and during competition. With these new spring loaded pistons, when you are extending the shaft, does a constant supply of pressure need to be added to the piston?

Meaning that when the piston is extended, is it still putting more air into it and having a constant charge to the compressor to keep it filled?

[DonRotolo]

With spring-return pneumatic cylinders I am familiar with, the usual practice is to extend the piston by pressurizing the cylinder (they usually have only one 'hole' for air) and then commanding your solenoid valve to "close", maintaining the pressure. You then open it when you want it to retract.

You might need a different kind of solenoid valve (compared to the KoP version) to do this.

[rcmolloy]

So when your maintaining pressure, the piston is basically being held in with a constant flow of air coming out?

If I could rephrase the question, can the piston have two fixed positions one being fully extended and one being fully retracted without having to keep a constant flow of air.

[Jared Russell]

When the cylinder is extended, the volume that the pressurized air in your pneumatic system must fill increases (because pressurized air needs to fill the inside of the cylinder behind the plunger). Once the entire system (on the working side of the regulator) reaches the desired pressure level, there is no need to keep the compressor running except to replenish any air lost due to leaks.

This goes for both double-acting and spring-return cylinders - once you are extended, all you need to do is maintain pressure.

[Jared Russell]

Originally Posted by rcmolloy

If I could rephrase the question, can the piston have two fixed positions one being fully extended and one being fully retracted without having to keep a constant flow of air.

Yes. Air only "flows" when you are in the act of extending or retracting the cylinder. Once it is in place, all you need to do is maintain a constant pressure level and you're golden.

[rcmolloy]

Ahhh ok. We weren't sure if they acted like regular pistons but it does. The spring just allows it to retract faster because of the "shifting on the fly" allowance.

Thanks guys

[jspatz1]

The cylinder will consume no air after it is extended, the pressure holding it is static. You will want to maintain extend pressure (valve actuated) so the holding force is maintained. When retracted (valve exhausted) the cylinder will be vented and the spring will supply the only return force. A spring return cylinder consumes 1/2 of the air (actually a little more than 1/2 due to the rod volume) of a double-acting cylinder.

[IndySam]

Think of it like a balloon. When you fill a balloon with air you tie it up and it stays full, you don't need to add more air.