Pneumatic confusion

[Archangel]

Anyone a pneumatics expert?

I have a pneumatic underpinner which has a fault, but the main problem I have is that I just don't understand how a certain part can operate from the schematic.

heres the schematic (page 13)

http://www.cassese.com/manuels/199%2...%20299MXL2.pdf

Here's what happens/supposed to happen

The "pre-clamping" knob is set to let air to the footpedal, so the pre-clamping piston is not being used here
1) You push the foot pedal
2) Air goes to the "or" shuttle valve (top right of diagram) and then on to the clamping piston which extends
3) The piston makes contact with the "security clamping" plunger (bottom middle of diagram) which sends air to the other "or" shuttle valve and then onto the 5/2 pilot/pilot valve, activating the valve
4) The air also goes to the "stapling button" when this is pressed air is sent through a pilot/spring valve activating it, removing air from the indicator "lamp", and allowing the valve from 3 above to activate, and also putting air to the bottom of the 5/2 pilot/pilot valve which because it is now active sends the "stapling" piston up
5) At the top of the piston stroke, the "end of travel" sensor is activated which should send the piston back down.
6) You release the stapling button and the process can be started again by releasing the foot pedal, or the button can be re-pressed and another staple is fired on top of the first one.

Now what I don't understand is how (5) actually happens? From the schematic, when the "end of travel sensor" is activated, air is sent to the "or" valve (which is already activated by the "security clamping" plunger in (3) above) and then on to the 5/2 pilot valve which is already in the activated position, i.e. it shouldn't have any effect, but I know it does!

Sorry for the long ramble, but I'm confused.

[mudskipper]

Anyone a pneumatics expert?

I have a pneumatic underpinner which has a fault, but the main problem I have is that I just don't understand how a certain part can operate from the schematic.

heres the schematic (page 13)

http://www.cassese.com/manuels/199%2...%20299MXL2.pdf

Here's what happens/supposed to happen

The "pre-clamping" knob is set to let air to the footpedal, so the pre-clamping piston is not being used here
1) You push the foot pedal
2) Air goes to the "or" shuttle valve (top right of diagram) and then on to the clamping piston which extends
3) The piston makes contact with the "security clamping" plunger (bottom middle of diagram) which sends air to the other "or" shuttle valve and then onto the 5/2 pilot/pilot valve, activating the valve
4) The air also goes to the "stapling button" when this is pressed air is sent through a pilot/spring valve activating it, removing air from the indicator "lamp", and allowing the valve from 3 above to activate, and also putting air to the bottom of the 5/2 pilot/pilot valve which because it is now active sends the "stapling" piston up
5) At the top of the piston stroke, the "end of travel" sensor is activated which should send the piston back down.
6) You release the stapling button and the process can be started again by releasing the foot pedal, or the button can be re-pressed and another staple is fired on top of the first one.

Now what I don't understand is how (5) actually happens? From the schematic, when the "end of travel sensor" is activated, air is sent to the "or" valve (which is already activated by the "security clamping" plunger in (3) above) and then on to the 5/2 pilot valve which is already in the activated position, i.e. it shouldn't have any effect, but I know it does!

Sorry for the long ramble, but I'm confused.

Not a pneumatics expert, but....

Your confusion is that the 5/2 valve for the stapling piston is active regardless of which side of the OR the air is coming from.

In order to deactivate it, you need air to come in via the the lamp route. That looks like it should happen on release of the stapling button.

Presumably (if you haven't released the foot pedal) the clamp piston, and therefore the security clamping piston is still active. So as soon as the 'end of travel' is released, the OR valve will flip again.

So is the end of travel sensor just a safety cut out for if you release the foot pedal with the stapling button still depressed and not related to the release of the stapling piston at all?

[Archangel]

Thanks for the reply. Your theory matches mine, but not the reality. The piston returns when the end of travel sensor is activated, even if you are holding the stapling button (well, mine doesn't, but it should according to others I have spoken to).

[mudskipper]

Thanks for the reply. Your theory matches mine, but not the reality. The piston returns when the end of travel sensor is activated, even if you are holding the stapling button (well, mine doesn't, but it should according to others I have spoken to).

You're a contractor - buy a new one.

[northernladuk]

I thought I had a similar problem with my tractor and my giraffe before I realised one has hydraulics and the other has high bollux

[Archangel]

You're a contractor - buy a new one.

I'm not a contractor anymore, and I can't afford a new one

[mudskipper]

I'm not a contractor anymore, and I can't afford a new one

Ah, you want http://www.PoorPermies.co.uk

[Archangel]

Ah, you want http://www.PoorPermies.co.uk

No, not a permie

I'm a real business, I am.

[DimPrawn]

I had pneumatic confusion.

Doctor said it was due my inflatable lady going down on me.