double acting cylinder actuators

by shirley
(india)

when do we use double-acting cylinder actuator for valves?


is there any advantage of double-acting cylinder actuator over single acting ? if so what?

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Bill says...

Shirley, if you are talking about using a double acting air cylinder versus a single acting air cylinder for operating process valves, where the air cylinders are providing the power to rotate large ball or butterfly type valves, then the choice between the two will be the power that is available.

A circuit may have a small ball valve in it, and use a single acting air cylinder to power open or close the valve, but when movement is required in the opposite direction, the absence of load allows the cylinder to operate the valve withe just the inside-cylinder spring providing the force.

If the valve actuator requires significant force in both directions, to both open and close the valve, a spring extend or retract air cylinder may not have the force necessary. A double acting air cylinder would.

So, any advantage of one type of air cylinder over the other will be based solely on the application.

Cheers,

Bill

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Rodless air cylinder being semi automated

by GGarner
(San Diego CA)

I am setting up a semi automated spray booth at my company (small company so I am doing it myslef)

I purchased a 6' long rodless air cylinder which will support the spray head/atomizer.

The question is I am having a hard time figuring out what type of switches to use and how to do the wiring. The air cylinder has a magnet in it so a reed switch seems to be the way to go. We want the trolley to travel to the ends of the rail so i imagine putting the reed switches where they trigger when the trolley gets to the end of its run. Then I want it to reverse direction and do the same thing at the other end.

I am new to pneumatics so I dont know what sort of a solenoid I should use. I am pretty sure that I need a 4 way 2 position solenoid but am unsure if i should use one with a single solenoid and spring or dual solenoid.

The more I think about it the more i think the dual solenoid would be the way to go.

Is my following logic correct given the following configuration:
Dual solenoid is plumbed as follows
In: from air regulator
Out: nothing... exhausts into room
A: plumbed for right to left motion
B: plumbed for left to right motion

The solenoid which activates left to right motion is wired to the reed switch 1 on the left side of cylinder

The solenoid which activates right to left motion is wired to reed switch 2 on the right side of the cylinder

Say the trolley starts out with path A (R to L) active it passes by the reed switch 1 firing the solenoid to activate path B. Then travels L to R activates reed switch 2 and the whole thing repeats???

In order to reduce any shock hazzard I am running 24V DC solenoid/transformer etc.

I am also curious about how to do the electrical wiring.
- from 24v transformer to reed switch 1 then to solenoid activating path A
- from 24v transformer to reed switch 2 then to solenoid activating path B
+ from all solenoids to + on transformer

___________________-
Bill says...

First off, for a spray application, either you want to find explosion proof or intrinsically safe solenoids to avert an explosion.

Your overall logic works, yet in your application, I would opt for an all pneumatic logic sequence to avoid the use of electricity altogether.

Either way you wish to go, setting up air circuits is something I do, but not for free. If you wish a quotation from me to prepare a circuit and drawings for you, please send in another ASK question with the words "need quote for logic" as the subject, so I can get to it more quickly.

Cheers,

Bill

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Air driven cylinders - Halloween exhibit

by david Henning
(Wellsburg, IA)

What i am looking for is some information on a air driven extending cylinder in order to make a halloween surprise scene for our community club haunted corn maze for next year.

What i would like to do is mount a frame to a cylinder so that it will pop up from the ground level with a ghoul on the frame to scare people.

It should have the capability of extending about 60", the height of a decent height ghoul. it would be nice to have a valve that would self exhaust the air and return to the ground level for the next scare with a delay of about 5 seconds for the scare. the frame and ghoul would weigh about 40-50 lbs.






Bill says...

Hey David:

Everything you'll need for this is available from your local compressed air components shop. Check the listings for air cylinder sales outlets in your area.

You need to know how fast you want the ghoul to pop up, and that will dictate how much air and air pressure you need.

What happens when someone is standing on or near this device and it triggers? You need to think hard about the safety issues.

In terms of an auto dump so that the display returns to ground level, that's fairly easy.

Again, what triggers it, and what are you going to do to make sure it doesn't hit someone?

Cheers,

Bill

Comments for Air driven cylinders - Halloween exhibit

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Dec 20, 2009
Hallpween Popups
by: Chuck

Take a look at the monster list at

Monster List.

There is a LOT of information about Halloween scares there, including compressed air powered props.

______________________

Thank you for that. Here's another source for Halloween scary stuff: Fright Props .

B.

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actuate a single acting air cylinder

by victor
(tulare)

i want to actuate a single acting air cylinder with two, two position air valves

i have a single acting air cylinder we are using to raise a catwalk and it is lowered with gravity and a regulator for speed control, we currently have one two way switch at the bottom of the stair case and we are wanting to add another air switch to the top of the stair case to raise or lower from either switches , what type of air switches will be required to achieve this?
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Victor, you need a bit of air logic, and air circuits are not free.

I can tell you that you can do it with a couple of 3/2 air valves, and an "or" gate.

You say you slow the gravity drop of the catwalk with a regulator? I'd probably use a flow control, myself.

Or, post a comment here telling me to, with your email address, and I'll send you an invoice for $75.00 via PayPal. When I get payment, I'll email you the circuit diagram with a BOM.

Cheers,

Bill

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