Air delay device

If fairy dust won't work, try sequence valves.

Bob

Tom, I remember using a Festo Pneumatic timer for just this sort of thing a few years ago. I've had a quick look around the net but can't locate the part number for it.It was adjustable from 0-10 seconds if I remember correctly. I put a tee in the line which extended the cylinder and used it supply the signal to the timer. At the set time, the output from the timer would come on. It worked really well.

That be the ticket, thanks!

Thanks, it looks like a pneumatic timer or a sequence valve will work. I didn't know what to call it.

On Mon, 11 Aug 2008 02:06:00 -0400, with neither quill nor qualm, "Tom Gardner" quickly quoth:

Damn, that ruled out all MY suggestions.

OK, one last idea: Why not use a positional valve? Once/as the large cylinder fits into place, it physically activates the valve which activates the cylinder.

-- Pain makes man think. Thought makes man wise. Wisdom makes life endurable. -- John Patrick

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There are a number of simple, adjustable pneumatic time delays out there. We use them on our semi-manual air presses to establish a "dwell time" after pressure has been applied to the load.

MSC part number #65242224 Parker/Rexroth

This one has a .1 to 3 second delay. Other delays are available.

LLoyd

We custom built a hand-help spotwelder years back for assembling steel panels on a hangar door. In series with the cylinder was a pressure switch, when the cylinder clamped up, the pressure in the line rose, tripped the switch. The switch closure was used to trigger the spot welder, but, in your case, could fire a solenoid valve that controls your bigger cylinders.

Relatively simple.

The timing is now controlled by the event itself.

If, then

Instead of relying on time, it seems it would be better to rely on actual position feedback which would be more reliable and potentially faster. I know I've seen pneumatic "microswitches" that could be used to enable the second cylinder when the first has reached the proper position.

But my inclination would be to use the positive feedback that says that the big cylinder is in place before you let it go. With open-loop timers you're depending on the little cylinder working in a predictable time, which means you have to design your time interval for the worst-case condition (probably low pressure and worn cylinder).

With a positive "I'm here" valve on the big cylinder position you'll always start the small cylinder in the shortest time.

Of course, you want to make sure that that feedback really only ever actuates when the big cylinder is really in position -- a paranoid design mindset would have you push on the big cylinder through a spring, and actuate it with the un-sprung rod from the little cylinder so that you know that the big cylinder is in position _and_ being pushed on before you proceed.

If you're not interested in learning about "air logic" then I suggest you purchase a 5030-06 or a 5030-05 ARO

3-way valve or their equivelant. These valves have a stem, which when pressed, allows air to pass through. The "-06 is a shart push-button actuator while the "-05" uses a wheel for actuation. Therefor choose the one which better matches your mechanical conditions.

Either of these valves will send air to the large cylinder when the stem is depressed; adjust your flow control to match.

dennis in nca

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

It sounds like you refered to the same cylinder twice.

Limit and air valve. Presure switch and air valve. Timer.

Then we need to think about the retraction sequence for the two cylinders.

Wes, who likes plc's.

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

I might have a project with some work that would interest you Wes. PM me and I'll send you a PDF of the system if you want a look see.

These are what we use where I work:

are a Legris threshold sensor. After 1 cylinder strokes out, the valve allows air to pass. Click on the "View the Flash animation" to see how it works. Very reliable for us.