Would a power beyond valve work?

[Cord]

In the next month or so I'm going to order a boom pole for my skid steer. The pole will have hydraulic extend. I'm going to have the company provide a mounting plate to which I'm going to mount a hydraulic winch. The winch will raise and lower a hook. The end result will be an attachment which will function like a hydraulic stick crane. I have a couple tasks for this attachment, some tasks require operation from in the cab, some require operation from the ground (machine is stationary). The skid steer is an older model so it doesn't have the built-in auxiliary electric controls. Instead, it has a foot pedal which operates a third spool valve. I thought about using an electronic control valve, however I need greater precision than a on-off valve could provide.

My plan is to mount a 4-way joystick control valve on the attachment. This valve will allow me to operate both attachment functions when the foot pedal is locked on. The problem is trying to select which of the two functions the foot pedal will control from inside the cab. I was wondering if a single spool latching valve with power beyond would serve this function? With the valve latched in position A the foot pedal would then control function A, with the valve latched in position B, the foot pedal would then control function B. With the valve in neutral, the foot pedal would then provide power to the joystick.

Is the is the correct valve for my application? Both valves should be "open spool", right?

 

[TMGT]

Do you need to operate both functions at the same time?
If not have you considered a diverter valve?

 

[Cord]

I thought about a diverter, but they can't supply a third circuit.

 

[TMGT]

What do mean by supply a 3rd circuit? You can stack them to provide multiple circuits from one control valve.

 

[jenkinsph]

For a hydraulic winch with a motor you would want open spool. If the boom extends with a cylinder you would want closed ports.

As TMGT points out you can stack diverter valves to provide multiple circuits and this is probably the most cost effective route to take.

Would also toss this out there, if you want electric solenoid valves that you can 'feather' then look at proportional controlled valves. These allow multiple control stations with multiple spools and are used on cranes and other automated equipment today. I bought a two spool Danfoss PVG 32 proportional valve about a month ago for machine control on my laser leveling set up. It allows for very small corrections in the cylinder to full on just like you would have with a manual control lever.

 

[Fallon]

For a hydraulic winch with a motor you would want open spool. If the boom extends with a cylinder you would want closed ports.

Wouldn't an open spool let the winch freewheel when not being powered? I understand the need for that on many hydraulic motor uses, like a rotary cutter that would need to spin down. However on a crane I'd want the winch to hold my load steady when not being raised or lowered. An open spool would let the load come crashing to the ground unless there was an additional brake or something on the winch.

 

[Cord]

For a hydraulic winch with a motor you would want open spool. If the boom extends with a cylinder you would want closed ports.

Can I use a closed center valve on a circuit fed from the machine if the machine's valve is open center? Yes, I would want the motor to help hold the load. A lock valve would work, but I'd rather not have one. I believe most valves can be ordered with load checks so maybe thats what I'd need to specify.

 

[Fallon]

Open spool is different than open center. Center refers to how the valve needs to be fed with constant pressure (closed center) or a power beyond loop (open center). Open spool refers to connecting both work ports together so the motor can spin freely & coast to a stop when the valve actuation stops.

 

[bigdeano]

I have a boom with a hyd winch on my loader that I used to pull well pumps. The winch is worm gear with a high ratio so it holds the load itself. I just run it from the rear remote on the tractor which has a cylinder type valve that blocks the work ports in neutral. It works fine because there's very little inertia in a winch.

 

[jenkinsph]

Can I use a closed center valve on a circuit fed from the machine if the machine's valve is open center? Yes, I would want the motor to help hold the load. A lock valve would work, but I'd rather not have one. I believe most valves can be ordered with load checks so maybe thats what I'd need to specify.

I would not depend on the hydraulic motor to hold tension on the winch. As bigdeano mentions a worm drive winch does not need it. What kind of winch are you using? This could make a difference in what you need but some winches use brakes and other methods to lock them down. A Braden winch with disc brakes and two speed planetary drive might need more hydraulic control than a simple single speed worm drive winch.

With a simple worm drive winch you could take the hoses off the hydraulic motor and the winch would not move. Works the same as a guitar tuning head, the worm drive locks the teeth from turning on the shaft/drum.

I prefer an open spool valve for hydraulic motors because it puts less stress on all the parts. That said you can get by with closed ports on the spool if the inertia is low as is the case with a worm drive winch. If you have a hydraulic motor turning at high rpm and shut off the flow with a cylinder valve that can put a lot of stress on the parts. In your application I would assume your winch will have a low speed motor similar to a Char Lynn orbit motor with speeds between 100 to 300 rpm that directly drives the worm gear. You can get by with either open or closed spool in this case if you "feather the valve".