Pneumatic Control for Conveyor

IMO you also need a mid piston position detection. You can solve that with your electric part or pneumatic (hydraulic). Need to give the system some intelligence.

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think i dont find the result as you have advised. i mean, i have now in my possession the 5/2 way sv and cyl, tried testing by all means to place the cylinder in the mid position during neutral, but cant do so. i mean is it the correct sol valve am using for this set-up? yap, am really in trouble and am suppose to find solution for this set-up by all means without perhaps using piston position sensor or whatever, just by simply using purely pneumatics.

thanks and very much appreciated

ok copy, i'll be waiting from you the solution. am really nid to have one. thanks for your help and much appreciated.

kind regards

Hi, you can take this method: Making use of magnetic switch, you can take it to the position you want.

hi ATC,

thanks, but are there no other way we can do without using a magnetic switch? just purely pneumatics configuration? i would rather prefer using this method as the last option.

thanks and much appreciated

Use 2 x 5/3 double-acting solenoid valves instead.

"Simples! ξ"

copy, PWSlack, would you mind if you could send me a diagram or configuration drawing for this?

thanks and much appreciated

How secure - (blocked?) needs your mid way position to be? What I mean is: do you need 1. Just a floppy stop or a repeatable steady position? 2. What do you have available to control? just a switch or are the positions part of a diagram in a automation circuit? It will not work without a position detector. Components needed will depend on your piston speed and frequency of cycling. Diameter of piston, size of manifolds, air supply available. If you want to use a magnetic reed contact or magnetic valve, it will need to detect the plunger position through the wall of the piston. If you can make the detection mechanically (on the course of the belt) your process might be more controllable. Do you control with pressure equipment only (servo) or with electric valves (and/or manifolds). These are questions to provide you with a correct diagram in stead of 10 guesses. Respectfully. D

copy, Tornado, i think this one will work. i never thought about these for an instance. i will try these one and really this will work. thank you so much and much appreciated.

also, thanks everyone who contributed thier ideas. i really learned a lot from all of you guys....thank you so much

"there can be no ignorance when you do not refuse to learn the knowledge"

You could do the same thing by using 2 x 3 port soleniod valves instead.

Each 3 port valve controls one side of the pneumatic cylinder

By energising both valves you will get the cylinder to the mid position, but it will not be instant. But it would have the same reaction time as using 2 pneumatic cylinders. Never tried it, but it would be reasonably quick, let me know how you get on.

This would be a cheaper option than buying another pneumatic cylinder, i think. And the engineering cost of installing it.

Cheers

Joe

May the force be with you.

I think that this arrangement would allow the piston to remain anywhere along its stroke; in other words, indeterminate position.

There is another method of using variable air pressure to work against a spring, but the OP didn't want any sensors or switches with the cylinder(s).

Dear Joe Sparky,

Your proposal ignores the area of the cylinder rod. With full pressure on both sides of the piston, the resulting force is the same as if the pressure were applied to the cylinder rod area only! It would be better to provide a centering spring and vent both sides of the cylinder to achieve centering.

Luther M

Measure the stroke from forward-neutral and neutral-reverse. Now take two cylinders of those strokes and connect them in series. Now, when the first in energized, the valve will go from forward to neutral. When both are energized, the valve will go the reverse. Depending on whether they are spring-return or double acting, you can switch back by releasing pressure or switching the cylinders.

A 2 position valve will only extend or retract the cylinder fully. A 3 position would give you your desired result, however, whether it is a centre exhaust or centre pressure or centre blocked is still a remaining consideration. A centre exhaust, will empty both sides of the piston and have the potential of creating an unsafe fast moving load when the advance or return sol is fired. Centre pressure will give equal pressure to both sides of the piston, which will keep the position wherever it was when the sol position went to centre, however this is only true if you have equal area on both sides of the piston (like a rodless cylinder) and if the hosing or cylinder has no leaks. For a rod type cylinder with unequal areas, you will need to use a regulator (with back flow option), on the side opposite from the rod, in order to reduce the pressure and keep the rod and piston from drifting. This is the safest system for long strokes where people may go near the load. A centre blocked solenoid will do just that in the centre position, it will keep any pressures that were in the cylinder at the time and theoretically maintain the position, but for safety reasons this is a bad option, as it has the potential for trapped air, that can result in sudden high speed movements when maintenance people are trying to work on it, even when the system pressure has been shut off and exhausted. Knowing all this, you will still only have a rough stop position based on timing of solenoid, and would need a shifting stopper and lock pin to safely hold the mid position, and a reed switch to feed back to the PLC of what position the cylinder is in.

We use a system on heavy equipment to control position of cylinder,using a rod attached to one end of piston that contacts an electrical switch to stop motion of cylinder at desired location

Valski, most manufacturers of spool valves offer 3 position valves. They are available with a center position that has options of all ports blocked, cylinder ports open to exhaust and cylinder ports pressurized. With solenoid or air pilot operators this 3 position spool is normally spring centered. With a manual operator (eg lever) the spool may be spring centered or detented in all three positions. Tom

gentlemen,

i will try to test all your recommendations which are all worthwhile. thank you so much for your interest on these issue and will give you feedback on the result soon.

once again gentlemen, thank you and much appreciated.