Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
(OP)
I am new to hydraulics but I have a unique problem. 4 telescopic SA - power up/gravity down cyclinders are lifting a stage platform. I used a gear type 4 way flow divider (delta) and that works great on the way up. The only problem is (outside of putting an elephant on the stage)the stage does not have enough weight to bring it down. Evidently, it takes a tremendous amount of PSI at each cylinder to start the gears turning in reverse) So I removed the gear flow divider and now it comes down easily but naturally it does not go up evenly at all. The pump is only 3GPM and does not use much pressure to lift the stage. How do I get these cylinders syncronized on the way up and have the stage come down? Any help would be appreciated.





RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
Something else is wrong with your system.
Please post a schematic, and verify that the system is built as the schematic says.
Mike Halloran
Pembroke Pines, FL, USA
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
Mike Halloran
Pembroke Pines, FL, USA
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
Other than installing a servo system, which is very expensive, the best way is to convert the cylinders to double acting, install some motion control valves, then use the flow divider to drive the stage up and down.
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
They are no where near a accurate as rotary flow dividers because they have excessive internal leakage. If you have one cylinder with a higher load, the higher pressure in the cylinder will cause more leakage and the cylinder will be slower than the others.
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
The design I currently have involves two compact hydraulic cylinders, spaced about 100mm apart, lifting a platform as distance of about 10mm.
Planning on using something like this wrench powered screw-pump http:
At this scale, would I still need something like a flow-divider to coordinate the movement of the cylinders?
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
The accumulators will have to be fully isolated though as there would be no way to safely top them up, not without potentially jolting the the stage.
Then, when the accumulators come in, they will need pressure compensated flow control valves to regulate the speed, otherwise the whole thing will come down too fast.
It would work, but may be a bit jumpy and very noisy. There is no noise like an over revved flow divider.
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
the pressure to lift the platform is maybe half of the pump pressure. precharge the accumlators just above this pressure. so as the stage lifts, all fluid goes to the pistons. once the pistons reach stop, then the pressure will increase to pump pressure and fluid will enter the accumulator.
the line from pump to divider is isolated to hold the stage lifted and the accumulators keep the pressure in the cylinders at pump pressure.
to lower, the line is drained. the intial pressure is sufficient to start the flow divider spining backwards. once the volume of the accumulator is exhausted, the pressure in the piston is reduced to just under lift pressure and the platform lowers as the divider reverse spins. the rate of decent is controlled by the opening of the drain valve. there will be a delay from opening the drain till the platform moves
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
If it works fine going up through the flow dividers and works fine coming down without the flow dividers, place four tees in the circuit - one on each line between the divider output and the cylinder. On each tee, place a check valve that allows fluid flow out of the divider-to-cylinder branch. Run all four of the lines (downstream from the check valve) to the pump side of the flow divider.
There will be no cross-communication between the lines while raising because the check valves prevent any fluid from entering any cylinder and the pump side pressure into the flow divider will always be higher than the pressure in the cylinders, which will keep the check valves closed. There would be no movement when stopped, because the cylinders are fully extended and everything downstream of the work port of the directional control valve is a closed system.
HOWEVER - this requires a directional control valve that has an integral check on the work port when the handle is in neutral.
Engineering is not the science behind building. It is the science behind not building.
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
Hey byrdj & EngineeringTex , Can you share a schem of the arrangements discussed?
I have a similar problem, I want to raise and lower a fixture using 4 hydraulic cylinders that need to be n'sync... the challenge for me is that the fixture is used on several stations and the load changes...
Hope you can share.
Happy holidays!
RE: Lifting platform stage with 4 hydraulic cylinders- How to keep in sync
CHECK VALVES
____________O>_______________________
| |
|____________O>_____________________ |
| | |
|____________O>___________________ | |
| | | |
|____________O>_________________ | | |
| | | | |
| | | | |
| | | | |
SOURCE -----------[DIVIDER] | | | |
| | | | | | | |
| | | |___________________|_)_)_)___________CYL1
| | | | | |
| | |_______________________|_)_)___________CYL2
| | | |
| |___________________________|_)___________CYL3
| |
|_______________________________|___________CYL4
TEES (4QTY)
Engineering is not the science behind building. It is the science behind not building.