Single acting cylinder (w/spring) extend and hold position under load

[BWSwede]

I am working on a project for remote control of a 3 point hitch winch running off the tractor's pto. I need to push a lever to power the retraction of the cable. To do so I need to send oil to a single acting cylinder that also has a return spring.

I am struggling to figure out how to fully extend the cylinder and hold it in the extended position without constantly sending oil to it (which would cause a bypass valve to open on the valve bank). This would be easy if I were standing next to the winch. Most of the time I control the winch I'll be at least 100' from the tractor using radio controlled solenoid valve to control the oil flow. It seems like I need a solenoid valve that acts like a log splitter valve on the return stroke, ie. feeds oil to the cylinder until it hit the end of the stroke then the valve kicks off and the cylinder holds in place.

Can anybody educate me on how to best accomplish this task?

Thanks in advance,
bwswede

 

[J_J]

A single action [ SA ] valve will do what you want.

You can also use DA valve for this,

You push the lever to extend and release to neutral for hold.

To retract, the spring will pull the cyl back.

My hyd press has a spring loaded jack .

You pump it up and it stays in place and when you turn the release valve, the spring retracts the rod.

 

[BWSwede]

J_J,

Thanks for the quick reply. Sounds good but I need a 12v solenoid valve since it will be radio controlled that does something similar. In addition, since I will be nowhere near the valve when I am controlling it I need it to kick off automatically when it hits full extension.

Thanks again,
Blane

 

[J_J]

So, what you need is a solenoid motor spool valve so when you press the extend button on the remote, the cyl will extend and when you let off the button, the springs will retract the rod.

A motor spool is normally used to allow a hyd motor to coast to a stop, so there is free flow in neutral.

They do not make a solenoid log splitter valve.

Prince does make a auto valve that after pushing two levers, the cyl will extend and at the end of stroke, the rod will auto retract and then go to neutral , ready for the next cycle.

A solenoid open center valve will extend the cyl and when you let off th enutton, the cyl stays in lace.

When you want to retract, just hit the retract button.

The relief might sound, but the cyl will retract.

You can plug the B port, or run the B port to tank.

 

[aczlan]

How much force do you need to apply? If it's not much, how about using an linear actuator such as 5.9" STROKE 12 VDC LINEAR ACTUATOR CW ?
Then you hold the "extend" or "retract" button for 10-15 seconds and it will run to the end of the travel and stop. You could also use a latching relay so you just hit extend or retract and it will go to that stop.

Aaron Z

 

[BWSwede]

So, what you need is a solenoid motor spool valve so when you press the extend button on the remote, the cyl will extend and when you let off the button, the springs will retract the rod.

Not exactly. I need a solenoid valve that when I push and hold the button on the remote the piston extends to full extension. At that point there needs to be a pressure switch, or detent, or something else to stop the oil flow to the piston regardless of me pushing the button or not. I don't want to use a bypass/pressure relief valve as a solution as it will cause heat to build up. And yes, when I release the button the springs need to retract the piston. The button has to operate like a dead-man switch. When I let off the piston needs to retract.

SHow much force do you need to apply? If it's not much, how about using an linear actuator such as 5.9" STROKE 12 VDC LINEAR ACTUATOR CW ?
Then you hold the "extend" or "retract" button for 10-15 seconds and it will run to the end of the travel and stop. You could also use a latching relay so you just hit extend or retract and it will go to that stop.

I am guessing about 500 pounds of force. A linear actuator will move too slow causing the clutch on the winch will burn up real quick.

Thank you,
Blane

 

[aczlan]

500 pounds of force? Are you sure its that much? Any pictures of the setup?
How much pressure does your tractor hydraulic system put out?
I have an idea:
It would use a 2 button remote, a 2 way solenoid valve and a double acting cylinder. To reel in the winch, you press and hold Button 2, then tap Button 1.

When you tap Button 1, that activates the electric solenoid valve (turns on a latching relay, the output from the latching relay goes through a N/O pressure switch and into the solenoid). Once the cylinder hits the end of its travel, it builds pressure until it trips the pressure switch (which de-activates the solenoid).

Button 2 runs a SPDT relay, the N/O side feeds the power side of the latching relay for Button 1 (so that you can only start retracting the cable if Button 2 is held down) and the N/C side feeds the "deactivate" side of the solenoid valve through another pressure switch.

So, when you let go of the deadman switch, it de-activates the winch and maintains the preset amount of pressure on the "de-activate" side of the cylinder (but the solenoid valve is only turned on when the pressure drops below the limit of the pressure switch, so you aren't hitting the pressure relief all the time).

Aaron Z

 

[BWSwede]

Aaron, wow. I am going to have to sit down and draw out each portion of your description to make sure I understand what you are describing. In the meantime the winch I have is a Farmi JL501. The force on the rope to engage the winch is a guess at the high end about 150 pounds when pulling my heaviest loads up steep ravines. Inside the winch the rope goes through a multi-pulley system to multiply the force on the lever. I came up with 500 from 150 x 3. My tractor puts out 2800 psi for the hydraulics.

I am trying to use the stock single action hydraulic cylinders for the winch activation and for the brake (second piston) because I can get them with all the mounting brackets to make the installation real easy. I also know that by doing this the pistons will have the correct travel. The reason I don't use the full Farmi system is because it is an expensive electro-hydraulic system that I don't need with my tractor.

If I can't figure out how to work with the factory available single action pistons with hydraulics then I think I would rather use a pneumatic system to power the levers on the winch. I have 125 psi compressed air on my tractor so getting air to the winch is real easy.

Thank you,
Blane

 

[aczlan]

Aaron, wow. I am going to have to sit down and draw out each portion of your description to make sure I understand what you are describing. In the meantime the winch I have is a Farmi JL501. The force on the rope to engage the winch is a guess at the high end about 150 pounds when pulling my heaviest loads up steep ravines. Inside the winch the rope goes through a multi-pulley system to multiply the force on the lever. I came up with 500 from 150 x 3. My tractor puts out 2800 psi for the hydraulics.

Makes sense.

I am trying to use the stock single action hydraulic cylinders for the winch activation and for the brake (second piston) because I can get them with all the mounting brackets to make the installation real easy. I also know that by doing this the pistons will have the correct travel. The reason I don't use the full Farmi system is because it is an expensive electro-hydraulic system that I don't need with my tractor.

Ok, how about this then:
Same wiring as above, but use a single acting solenoid valve on the "winch in" side and put a tee between the solenoid and the cylinder. On the 3rd port of the tee, put a N/O hydraulic solenoid (such as HYDRA FORCE 12 VDC N.O. SOLENOID VALVE ) and run that line into the tank line of your power beyond (or directly into the tank).

When you tap Button 1, that activates the electric solenoid valve (turns on a latching relay, the output from the latching relay goes through a N/O pressure switch and into the solenoid). Once the cylinder hits the end of its travel, it builds pressure until it trips the pressure switch (which de-activates the solenoid).

Button 2 runs a N/O SPST relay, the relay feeds the power side of the latching relay for Button 1 (so that you can only start retracting the cable if Button 2 is held down) and the N/O hydraulic solenoid linked to above.

So, when you let go of the deadman switch, it de-activates the winch and opens the valve to "dump" the fluid from the cylinder into the tank (that way even if the "retract" solenoid fails open, you wont pull the cable in).
I can probably draw something up tonight if you want.

If I can't figure out how to work with the factory available single action pistons with hydraulics then I think I would rather use a pneumatic system to power the levers on the winch. I have 125 psi compressed air on my tractor so getting air to the winch is real easy.

Now you have me curious, what tractor comes with 125PSI air onboard (or did you add it?)

Aaron Z

 

[bigdeano]

Here's the simplest way I can think of to do this. Activate a double acting solenoid valve (2 coils) with a double pole relay controlled by your pushbutton switch. The relay would normally activate the valve to release the cylinder when button is released. When button is pushed, relay would power other coil through a time delay relay to actuate cylinder. When time delay is reached valve would return to center, holding cylinder in position. Set time delay just long enough for full stroke.

Only 2 parts needed besides solenoid valve, and no extra plumbing. You want a delay on open time delay relay.

You could use a normally closed limit switch on the cylinder to open the solenoid circuit instead of the time delay relay.