I need help designing a circuit that will extend and retract a cylinder continuously. I would like to be able to set the force applied by the ram.
So I have are a single spool pilot operated spring return valve 4 way. My question is should I use one pilot operated relief valve to charge the spool (Relief pilot pressure taken from the cylinder extend pressure). This would shifts the spool so the cylinder would retract and when the pressure builds on the completion of the retraction it charges another pilot operated relief to drain the spool thus allowing the spring to return the spool to position one?

One other quick question. Can you place a hydraulic motor inline using check valves so only when double acting cylinder is returning the force of the fluid turns the motor for basically a sequenced operation?

Or am I just nuts?

Thanks

You can contact your local Fluid Power Distributor Salesman and they will be happy to design your circuit to get a sale. Did that for years before I retired.

Now I design circuits for $125.00/Hour, 8 hours minimum.

OTOH, if this is a school assignment dig in and learn a lot for the effort.

You can see a Basic Fluid Power Ebook I used to teach Fluid Power. There is a link on the Home Page of this Forum. It covers what you call a Relief Valve, actually referred to as a Sequence Valve, in Chapter 14.

Thanks Bud. For that little bit of information opened up a whole new prospective. After reading the Fluid Power books, I just couldn't get the thought out of my mind that an uncompromisable fluid unlike a gas would be able to push a spool past its center or dead zone if controlled by an sequence valve on the work side of the spool. Then it hit me. I probably need two four ways using the smaller 4 way triggered by a Sequence Valve in the cylinder line, thus shifting main 4 way spool. This has both 4 ways supplied off the pump side.
Quick question though about Sequence Valves. Lets say a the valve has a adjustable relief setting from 150 to 2000 PSI. That adjustment is a correlation between the pilot area and spring strength. Lets say I needed 2600 psi max relief. Would it be just a matter of increasing the spring length or compression strength to meet that pressure vs resistance?

Thanks

Davis

quote:

Lets say a the valve has a adjustable relief setting from 150 to 2000 PSI. That adjustment is a correlation between the pilot area and spring strength. Lets say I needed 2600 psi max relief. Would it be just a matter of increasing the spring length or compression strength to meet that pressure vs resistance?
Thanks

Most manufacturers of Pressure Control Valves offer different pssure ranges for their valves. The pressure change is accomplished by using springs of diferent Compression Strength.
The bad part of this is a spring can be changed but the valve part number still shows the old spring information. If the old valve is replaced with the original spring the circuit will not perform as before.
You can look in a manufacturers catalog to see the springs available and how it changes the pressure setting capabilities.