Hydraulic valve selection assistance requested

[Cord]

I'm in the planning stage to build a hydraulic press. I'm looking for a valve that has a specific function, but I don't know the technical name of what it is that I'm trying to find. That's where I hope you guys can help. The valve I want will have this function: cylinder extends manually and will automatically spring back to retract when the lever is released. The cylinder will continue to retract to the end of it's stroke and then spring back to neutral. I'm guessing that some type of return detent would work, but I don't know how to get the valve to automatically shift from the extend position to return which skipping over neutral.

I thought about a log splitter valve, but those valves spring to neutral when the lever is released from the extend position. Close, but not quite right. An auto cycle valve will not work because they require two handles to be activated.

 

[ptsg]

If you can't find exactly what you need, you can also use a regular double acting valve, and build a mechanical linkage to achieve what you're looking for.

Use a heavier spring that can overcome the spring on the valve, then when the press fully retracts, it pushes on a rod that will return the valve to neutral. Or just remove the springs on the spool to make it easier to operate since you wouldn't need such an heavier spring on the linkage.

Depending on the use of the press, this rod on the linkage can also be adjustable in length so you can have different positions when retracted, instead of going all the way back, every time.

That how some log splitters are setup in my country. Not many actually use a log splitter valve.

 

[LD1]

No such valve exists that I am aware of.

The neutral position becomes the issue. Whatever mechanism that causes it to return to retract stroke and skipping over neutral....would want to constantly be trying to retract. IE: retract...pressure kicks to neutral...try and retract again....kick to neutral.....over and over again.

Wondering why you cant simply use a logsplitter cylinder and engage reverse yourself? Also wondering why you want it to auto reverse. I have used alot of hydraulic presses.....and auto reverse would be a PITA. You are holding the lever....getting things close and lining them up...take your hand off lever to make slight adjustment and it retracts all on its own.

Also....somethings I like to hold a little pressure on then smack with a hammer rather than try brute forceing something.

What you want "can" be attained with a 4way 2-pos valve that is spring return. However that would require a closed center system and a variable displacement pump

 

[ptsg]

Here is a good view of the linkage that I suggested on post #2. Note the axe hitting a rod when retracting, pushing the lever to neutral. Then the operator uses a foot pedal to move the axe forward again. This falls exactly on the requirements of the OP.

 

[Cord]

That's exactly what I want for a function. I must have watched that video a half dozen times and I can't figure out the mechanics. I see that it's a three position valve. Probably a splitter valve because of the pressure detent release on the return stroke. But how does he activate the return? As pointed out above, somehow reverse is triggered until the pressure detent activates and returns the valve to neutral without it reengaging reverse.

 

[Cord]

I have used alot of hydraulic presses.....and auto reverse would be a PITA. You are holding the lever....getting things close and lining them up...take your hand off lever to make slight adjustment and it retracts all on its own.

This would be for a forging press so you need to make repeated close-open motions in rapid succession. Many are doing this with two foot pedals, but the motion is slow and clumsy. A hand valve would the best solution, but that takes away one hand from holding the red hot piece of metal.

 

[ptsg]

That's exactly what I want for a function. I must have watched that video a half dozen times and I can't figure out the mechanics. I see that it's a three position valve. Probably a splitter valve because of the pressure detent release on the return stroke. But how does he activate the return? As pointed out above, somehow reverse is triggered until the pressure detent activates and returns the valve to neutral without it reengaging reverse.

It's a simple double acting valve but it does have a spring return, so the valve goes to return when taking the foot of the pedal. This can be done with an external spring as well that can overcome the factory spring on the spool or by modifying the way the factory spring works as on some valves is as simple as removing a washer there.

Here is a picture. Hopefully it's easier to see. Green arrow is the valve, blue arrow is the contact point to the axe when returning and yellow arrow is the rod connected to the spool. Once it retracts, pushes the rod and returns the spool to neutral.

 

[LD1]

So it appears that basically there is a spring that forces the lever into reverse and the valve, with no outside input, always wants to go to reverse.

The only way to get the valve out of reverse is using your muscle to pull the lever and overcome said spring.....or a linkage on the ram that when retracted all the way overcomes the spring.....but only enough to shift to neutral and not forward again.

Sounds doable

 

[Smokeydog]

My press and Enerpac maintenance tools are 10,000psi hydraulics.

Tractors and log splitters about 3,000psi.

Be sure your using properly rated valves, lines and cylinders. Significant cost difference.

Either one can have high load ratings but the components are different.