Hydraulic delay circuit

[RPW]

I have a project where I need to extend a cylinder and wait for a lever to trip the retraction of the cylinder. On another circuit I can use a log splitter valve with an automatic return but on this one I need to wait until an action takes place before I retract the cylinder. I was wondering if I held the same type of valve in the extend position until the action was completed would that work? This is for a tilt table and I need to wait until the material has cleared the table before tilting back to the original position.

Thanks in advance.

 

[oldnslo]

If this will be all mechanical.

Does the table unload via gravity?

What will start the cylinder to extend?

Will the empty table load always be the same?

Any estimate on operating pressure required to raise and hold the empty table?

Pressure required to raise a full table?

Does the tilt return via gravity or does require hydraulic pressure to return?

Depending on the difference in pressures you might be able to use sequence valves.

If electrical operated is an option you could use a time delay relay or some type of sensor to indicate when the table is empty and then retract the cylinder.

 

[CCWKen]

Now there's a process engineer at work.

 

[RPW]

oldnslo - I'd prefer it to be mechanical as an electrical connection is not guaranteed. Not afraid of electrical as I've been doing that in some form or another for over 50 years. Everything is done by hydraulic. Table tilt, table retract etc. Table load will be for the most part the same. There could be some variance but at this time don't know the extent. Pressure will be approx. 2500psi. Don't know how much pressure it's going to take to raise/tilt the table. Approximate weight on table will be ~400 lbs. I'm not real familiar with sequence valves. Just started learning about them.

 

[oldnslo]

RPW,
Sequence valves shift at a preset pressure point. Problem I can see is getting the circuit set up so that at a falling pressure the sequence valve shifts and allows the tilt function to retract or return to the home position.

If this was my system I would start by writing down a sequence of events for how I would I want this to work.

Then I would look at each event and try to determine what I could use to signal the end of that event and start the next event.

Doing this helps me identify what I want to do and what I functions I have to work with.

I agree with mechanical Vs electrical for simplicity and reliability but then I am also an old phart

 

[muddstopper]

A little infro about sequence valves, Sequence Valves - YouTube

 

[RPW]

Thanks, I did do a flow chart to help me determine what and when the actions were to take place and all went well until this circuit. I thought about a log splitter valve with auto cycle and was wondering what would happen if the lever was held in the extend function for the duration that it would require to empty the table. I don't think it would be very long but it could be a few seconds, maybe 10 to 20 at most. One thing I thought of would be an additional pressure relief valve to keep from deadheading the circuit.

 

[RPW]

Mudskipper, great video. Thanks

 

[oldnslo]

From what you described this will be a challenge. I like keeping things as simple as possible and I don't see a simple solution for this.

will think about it some more I am sure.

 

[RPW]

Oldnslo- Were you able to clear some cobwebs about a delay circuit or do you think an action on then action off might work. What I mean is think of a box passing by a sensor in this case it would be a trip lever and after the box passed it would trip another lever. First lever would extend the cylinder and the second would retract the cylinder. Definitely a brain twister.

 

[katoomed00]

You might look into hydraulic proximity switches. I only have experience with pneumatic ones and seems to me the hydraulics ones would work just as well.

 

[oldnslo]

Oldnslo- Were you able to clear some cobwebs about a delay circuit or do you think an action on then action off might work. What I mean is think of a box passing by a sensor in this case it would be a trip lever and after the box passed it would trip another lever. First lever would extend the cylinder and the second would retract the cylinder. Definitely a brain twister.

Problem with anything mechanical is the delay function unless the table is always empty when the tilt cylinder / table gets to a certain point. The a mechanical lever or cam operated valve could be used. Just have to figure out how to maintain the flow path during the cylinder stroke and then unload the pump at end of stroke.

Is the delay not needed or were you trying to limit the number of cams or levers you need for the operation.

 

[RPW]

Basically what is taking place is when the table is full it tilts to dump the contents in an accumulated state (it's hay). I don't know how long it will take to dump the contents. I've given some thought to using an SA cylinder but don't know if the table would return fast enough In time for the next bales to start loading onto the table.

 

[jenkinsph]

I would think a cheap photo cell setup as used on garage doors should work to detect when the table is cleared. This would allow you to use simple solenoid valves to operate the table. Might need a few well placed limit switches too.

Timing may work as well but if for some reason the table does not clear a photo cell would stop the operation indefinitely until the table was cleared.

 

[Leejohn]

I know you guys are talking hyd,but what about a spring loaded table and have the spring adjustable so you set it for the load you want.

 

[oldnslo]

RPW,
Since this for hay will it be sitting stationary or being pulled behind a baler?

Likejenkinsph says electrical would be relatively easy if explosion proof or fire hazard isn't an issue. If explosion or fire is a concern then electric gets significantly more expensive.

Could some type of lip or lever be installed on the table that would trip as the hay passes over it and then be spring loaded to return home once the table is empty? If this could possibly be tied to a mechanical valve to return the table to the home position.

 

[RPW]

Pulled behind baler. Electrical is possible but not always available. Example if I borrowed my neighbors tractor an electrical connection isn't available so that is why I'm looking at a hydraulic solution if possible. Also trying to keep it simple.

 

[oldnslo]

What supplies the hydaulic power to this collector tilt table? Tractor hydraulics or external power source?

 

[aczlan]

Do you have a picture of this beast, or a make/model number?

Aaron Z

 

[RPW]

Was planning on tractor hydraulics as the PTO will be used for the baler. So far it's still a picture in my head.