Pew Matics - High Drawl Icks and synchronized lifting. 3

[itsmoked]

So, I'm faced with lifting an object(lid) using either air or water-based hydraulics.
Do you guys have any ideas how you'd lift this thing -evenly- with 3 to 5 gas/water cylinders? (Approximately 2" per sec.)

Are there any companies that have O.T.Shelf servo controllers for this type thing or should I gab a PLC and try to roll my own? I'm sure Gunnar will suggest an "Arduno". LOL



Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

They would take an extremely dim view of any photos. The security guards would crush my camera and then make me eat the pieces.. Then they'd force your name out of me and nuke Silicon Valley telling everyone you caused it.




Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Reckon they could nuke Sunderland instead...?

 

[mikekilroy]

nice reply itsmoked; nps

seems weird your customer is being cheap on this; most government jobs we've done had more than enough money to do it right.

sure seems 4pc moog servo valves (internal spool moved by internal ballscrew) run by stepper with nice dithering servo valve driver cards in your plc is right answer, since they don't want really proper solution (4 brushless ac servo driven electronically geared food duty (no contaminating grease) linear actuators)

http://www.KilroyWasHere<dot>com

 

[itsmoked]

Hi Mike,

Got a link to said linears? Maybe I can sway them to the right solution.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Sparweb]

How about... Separating the "lifting" function from the "controlling" function.

Start with 3 hydraulic cylinders that simply lift. They have no control or feedback or anything. Arranged at 120 degrees around the perimeter of the lid (I'm imagining a big round pot lid for this example)

Then add 1 hydraulic cylinder remote from the container, that is fixed to the floor and holds 3 steel cables. Each of these cables are routed along the floor and then up to the lid. They hold the lid DOWN.
Slowly advance the cylinder that holds the cables, allowing movement of the lid as the 3 cylinders lift it.

The 3 lifting cylinders are sized that they cannot lift the lid until the cables move. The cables move in unison because they are all controlled by the same cylinder. The lid lifts straight up because the lifting cylinders are always in equilibrium. They can even slant in at an angle if it will help.

I think there is work to be done sizing and selecting the cylinders, valves, cables, etc., but I don't think it will need a "brain". As for lowering the lid back down, the same 3 cylinders can "pull" it down, but you will need 3 cables from above to hold it up. Could be a separate cylinder above that lowers it down, or route the cables to the reverse stroke of the control cylinder on the floor.

Also: can the lid be centered with vertical linear guides? The guides would center it vertically on the pot, though it wouldn't help keep it horizontal, I admit.


STF

 

[Compositepro]

So how about one hydraulic cylinder pulling on three cables that go over appropriate pulleys?

 

[waross]

Compositepro you took the words out of my mouth. That arrangement works well for a type of automotive hoist. One cylinder pulling four cables that lift the four corners.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

And, using pulleys, you can use a cylinder with 1/2, 1/3, or 1/4 of the stroke length compared to the lift height of the lid.

 

[itsmoked]

Ah, I love the ideas you guys are coming up with. That weak-and-leading-cylinder scheme is crazy easy. I like it.

And Sparweb, it is exactly a large "pot lid".
Alas, I doubt they'll consider cables of any type. I'll see.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[MikeHalloran]

Ordinary wire rope requires lubrication, or it rusts, and pieces of rust fall off. Not good.

They might be amenable to the plastic- coated wire rope that's used for boat steering. Unlubricated Delrin pulleys would be my first choice, atmosphere allowing.

For the lifting cylinders, you might be able to use gas struts, if you can find them with a long enough stroke. They typically have ball joints on both ends, so you may need to clamp the body or provide other guide means, e.g. a linear slide on one edge to provide trajectory control.


Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

How do they lift it now, or is this a new build?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Sparweb]

"Ordinary wire rope requires lubrication, or it rusts, and pieces of rust fall off. Not good."

If the stretch and sheave size requirements can be tolerated, Dyneema/Technora are synthetic rope materials to consider.

I have been told that plastic coated wire is useless for many tasks, including cases where the cable flexes under load.

I realized after posting my original idea that reversing the cable-driving cylinder is all that's required to close the lid again.

Instead of cables, you could have rods and bell-cranks. That would allow the one driving cylinder to be located "anywhere" and still apply 3 equal forces and displacements (with proper design) combined at 3 points on the rim of the lid. Bell-cranks don't allow a long displacement, though. How far does the lid have to move?

Is chain out of the picture? Even if grease-flinging bicycle chain won't do, aren't there 1001 other types of chain out there in the wide world of technology?

STF

 

[itsmoked]

Bill: New build.

Spar: This is a production semiconductor machine that probably costs between 3~5 million bucks. It will operate in a low number clean room. (as in class 100 or 100 particles per cubic foot.) No deodorants, no hair sprays, and no Axe(crap). Nothing that can cause dust, fumes, stray hydrocarbon molecules, etc., etc., all are strictly verboten. Hence their request for pure water or purified specific gas operated cylinders.

The machine has lots and lots of stuff happening on it and in the room around it, above it, and under it. It has dozens of gas lines, power lines, sensor cables, and RF signals, routed to it and across it. This is probably why they don't want to complicate the area around it with overhead cables or underneath cylinders that all carve out "exclusionary spaces" around the vessel.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[mikekilroy]

google "clean room linear actuator"

Lot of choices. The IE intelligent actuator models have very simple controls available too and have been around for a long time (we reped them back 25 years ago):

http://www.intelligentactuator.com/robo-cylinder-cleanroom-slide-type-electric-actuators/

http://www.KilroyWasHere<dot>com

 

[itsmoked]

Thanks Mike. I'll see if those might fit.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ewh]

FYI... The Moog (rhymes with rogue) valve company founder is not involved with Moog synthesizers (or Moog suspension parts)... but he did patent a nifty ski strap release!

“Know the rules well, so you can break them effectively.”
-Dalai Lama XIV

 

[ScottyUK]

Thanks for the correction ewh, t'was his cousin. Obviously a clever family!

 

[BrianE22]

With any over-constrained (more than 3 lifts) systems you run the risk of one or more actuating devices developing a large load if the system is stiff. You'll need to look at the compliance of the system. You may need a combination of stroke and load control.

 

[makesparks]

Hmm. I arrived late to this thread, but could you not use "standard" hydraulic components (versions suitable for use with water of course)? A gear type flow divider with a rephasing cylinder should work well. The hard part will be finding parts made for water service.

Link <-- Ways to synchronize hydraulic cylinders