Pneumatic End of stroke / threshold sensor 2

[bamia]

Hello guys and gals,

I have several questions all relate to pneumatic devices on two unrelated equipment.

First. images number 1 and 2 are of double acting cylinder and a valve with something in front of it that I could not figure out, I believe the manual lists it as "threshold sensor", is this what is called end of stroke sensor and how does it operate?

The cylinder end has thread that goes into the end of a tube and it is pretty damn tight, the tube is stainless and inside it on that end looks like plastic (PTFE maybe) and there's a port in it. The port has a hose out of it that goes back to that box in image 2. The idea is that the cylinder would cycle back and forth none stop, it retracts all the was and somehow that hose going into that port makes it extend again. That is the problem, it does not extend.
So I disconnected the hose from the port and every time the cylinder retracts I momentarily block the hose end with my finger which would extend the cylinder and so on.
I hope that is enough information and hope someone explains to me how this part of the equipment functions?
I should mention that I removed the fitting on the port and put my ginger on it while the cylinder was moving back and forth and did not feel any pressure or vacuum, pretty much nothing.

Images 3 and are in another machine and I would like to know what the function of a circuit bar and I am guessing image is of pilot operated valve.

I know very little pneumatics so anything will be helpful.

Thanks a lot

 

[srini1785]

What is the application?. Some sort of volumetric filling?.

From the pics, i can only figure out that there are no solenoid or reed switches involved so its a pure pneumatic circuit. A threshold sensor is a pneumatic signal generator which sends out a pneumatic signal every time the cylinder pistons comes under it. Technically its a 3/2 way valve. Its possible that this sensor is connected to the pilots of the MAC valve (in image 3) thereby building a oscillating circuit which is used in various applications like pumping or punching.

The mac valve which you have shown in image 3 is a double pilot valve. I suggest that you make a rough circuit diagram by just tracing the tubes.

PS : The model number is not clearly visible. So suggest that you type it down for reference.

 

[bamia]

Thanks srini1785.

Yes, one is called hopper topper by unifiller.
The images I posted are not in the order I intended so to clarify, the image of the cylinder and tube and the image of the control box with the valve belong to the hopper topper. Let's not worry about the other two item.

The cylinder oscillates as you mentioned using some sore of a pilot switch, what I do not understand is how does the port I marked on the picture work, it is outside of the cylinder so how does the cylinder pressure or lack thereof get to that port? There's got to be internal pathway os some sort. And why I don't feel any change when I put my finger on the port and operate the cylinder?

 

[srini1785]

"The cylinder oscillates as you mentioned using some sore of a pilot switch, what I do not understand is how does the port I marked on the picture work, it is outside of the cylinder so how does the cylinder pressure or lack thereof get to that port? There's got to be internal pathway os some sort. And why I don't feel any change when I put my finger on the port and operate the cylinder?"

Can you please repost your image that you are referring to?. I am able to see only a red spot and the text is not legible.

I saw a video of "hopper topper" and i can tell you that these would be custom built for this OEM (Unifiller). So, it may not be possible to understand how it works internally and anything at best would be a guess. Anyway, the best method to understand the working would be through a circuit. Just make a block whenever you are in doubt and follow the tubes.

 

[Compositepro]

Pneumatic cylinders can be made into "air motors" by incorporating small poppet valves into the cylinder ends. When the piston hits the valve, a momentary pressure signal is sent to the pilot port of the directional valve, causing the air cylinder to reverse.

 

[bamia]

Thank you very much.
srini1785, it is custom built and I am attaching the manual of the current version of what I have.
I have contacted the manufacturer and order a seal that is work and affected the pressure going to what they called threshold sensor.
It doesn't look like I can attach a file so here are images of a couple of pages.

Thanks again.