little hydraulic cylinders

[greycloud]

Hi

I was looking to get small hydraulic cylinders that can be actuated by 5 newtons of force or similar, anyone know where I can find such cylinders?

Thanks

 

[BrianPetersen]

5 newtons??

What sort of operating pressure are you envisioning, and what sort of dimensions are you envisioning?

Back up, way up, and tell us "the big picture" of what you are actually trying to do with this cylinder.

5 newtons actuation force at (let's say) only 10 bar pressure (more than typical pneumatic systems, less than typical hydraulic systems) is just 5 square millimetres.

Anything that tiny is going to be custom made.

 

[Compositepro]

Seal friction will over-whelm your 5 newtons. You need to look at seal-less actuators like a bellows, diaphragm, or Airpel air cylinder.

 

[greycloud]

You can find pneumatic cylinders operating at even 1.6 newtons, they have what they call low friction cylinders; but thing is I preferred hydraulic cylinders since liquid is not compressible.

I want this cylinder to be actually moved by low force, much like what you do with a syringe but with even lower friction.

 

[hydtools]

If the required stroke is short, a bellows or diaphragm device would be low friction.

Ted

 

[greycloud]

well my required stroke is 30 mm only, I'm indeed looking for bellows as well.

 

[3DDave]

"small hydraulic cylinders that can be actuated by 5 newtons of force or similar"

0.01 mm diameter? 100,000 psi? The force is only one of several conditions to specify the performance. At least we have a stroke, but not a fully compressed length.

 

[TugboatEng]

I can't make specific recommendations about the cylinders but you really need to focus on the fluid as well. Most hydraulic cylinders using oil have buna-n seals which swell slightly in mineral oil. If you do intend to use buna seals you should consider silicone based oils as they'll provide a more consistent seal resistance.

 

[BrianPetersen]

It would sure be nice to know what the original poster wants to do with this cylinder. Move an instrument needle? What is the application?

 

[greycloud]

I did alot of research and it's clear I can't find a hydraulic cylinder with a breakaway force of 5 newtons.

I'm going for pneumatic cylinders which easily have the rated breakaway load I need.

I also ordered some bellows since they don't have seals causing friction as well.

Thanks alot for your assistance

 

[Alan Hitchcox]

Another option you might consider is a rolling diaphragm cylinder. They generally are actuated by air, but liquid can be used if pressure is not high. Most are single acting, so they rely on a spring or gravity for the return stroke. Some manufacturers offer a double-acting design.
They do not have any dynamic seals because the fluid is enclosed within a rolling diaphragm.

I suggest going to controlair(dot)com to see examples.

 

[btrueblood]

We do a lot of rolling diaphragms in my company. Seal friction per se may be negligible, but the seal convolution still has loss properties (bending of the rubber diaphragm wall) that must be overcome to drive the piston.

Sister company does a lot of bellows. Bellows have to have a stiff enough wall to not expand under the applied pressure differential and blow out the convolutions. If the wall is stiff enough, then the bellows have a spring constant that will affect the force required for a given displacement, i.e. the force will increase/decrease with stroke distance.

TANSTAAFL. Translation: there ain't no such thing as a free lunch.

edit: there are ways to do similar motions, look at brake master cylinders, hydraulic valve controllers, carburetors...other devices from the 30's and 40's. The idea is to allow seal leakage past the piston (very low drag piston seals), and have a way to recycle the leaked fluid back to a reservoir. Gets tricky if you need a double acting device, but I can think of a few ways to do it provided you have external power. Pneumatic controllers use the same concept, but they just consume (leak) a little bit of air continuously.

 

[LittleInch]

Well we know the force (5N), the stroke (30mm) but no idea about piston area or pressure being created by this 5N force.

Also what causes the piston to return to it's previous position?

Makes a difference.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.