Using Hydraulic Cylinders In Series

Sounds like some sort of hydraulic steam engine thingy....

http://www.liveauctioneers.com/item/16960780_brass-hydraulic-model-of-a-steam-engine-circa-1850

Why waste energy with intermediate pistons?

Have you thought this through?

Hi Lyn,

I am here for advise and open to suggestions of how best this can be achieved.

Thanks

Krish

Here's a good online resource:

Fluid Power Ebook, Edition 1: Fluid Power Basics

http://hydraulicspneumatics.com/ebooks/fluid-power-ebook-edition-1-0

Fluid Power Ebook, Edition 2: Fluid Power Circuits Explained

http://hydraulicspneumatics.com/ebooks/fluid-power-ebook-edition-2-0

Combined displacement is parallel rather than series.

A jackhammer can be an example of a reciprocating hydraulic device.

Thanks Tornado, I agree that combined displacement is indeed paralle. Let me readup on the Jack Hammer principle. If you have any material it would be helpful too.

Thanks

Krish

http://www.explainthatstuff.com/jackhammer.html

I've seen electric jackhammers and pneumatic jackhammers, but never a hydraulic jackhammer. Are they used in some particular industry?

I think most are probably pneumatic, but there are hydraulic types used as tractor and backhoe attachments. Either way, the valve sequence for reciprocating motion should be similar.

Thank you and Yusef1 for the stimulation of my brain. Once the image of a pavement breaker formed in my mind, it was as if I had just woken-up. Maybe it's Alzheimers.

hydraulic jack hammers are very common, and are used mostly at attachments on large equipment. But not always...here is one for instance which is designed to be used just like a standard everyday jackhammer one would see on any construction site.

Hi

You do not say why you want to adopt this kind of system and what you hope it will achieve. Cylinder action from one to another is uncommon but if you wish to get syncronisataion or stepped strokes i.e multiple increments is is done, but rarely. This is because you will be bound to get some out of syncronisation at some point and it is necessary to build in either a manual or automatic reset to get all cylinders back to a base.

A typical application is the movement of two feed trays into a press. As one goes in the other comes out so you use one to drive the other. In this way they must be syncronised. If one arrives before the other you can arrange an auto top up of the slow unit. Provide some more information and I will try and assist you.

Regards

Oliver Dunthorne (Hydraulic engineer - retired)

Have you considered using one cylinder of equivalent piston surface area instead of the several cylinders in parallel? This would make the total weight of your unit lighter but not reduce the force generated by it. Also its physical size and weight would be less than the several cylinders because the shape with the greatest area and least perimeter length is a circle. The surface area is proportional to r². (one cylinder at 2 sq. inches (radius of 1") has a piston area of 3.1 sq. inches. To double the force a piston of 6.1 sq. inches is needed, which is provided by a piston with a radius of 1.6".

Or just get rid of the smaller hydraulic cylinders and directly pipe the fluid to the bigger cylinder. This will reduce fictional loss and provide better efficiency. The several small cylinders driving the larger cylinder also takes up more space and makes the device much more complicated. The motto of efficient, less costly, easier to design, easier to build and to repair engineering is KISS, "KEEP IT SIMPLE, STUPID!"

Good Luck, Old Salt

Hi Old Salt,

Totally agree with your suggestion to keep it simple. Unfortunately the smaller cylinders are spreadout over an area therefore consolidating them into a single cylinder will not be possible. I have attached a rough sketch below to explain what I am trying to achieve. My challenge is the automatic return of the Master Cylinder (MC1) piston back to its normal position (T0) once it has traveled to its maximum position (T1). The slave cylinders (SC1-SC3) are spring loaded to make them return back to default position once the pressure source is removed. Hope this clarifies the requirement.

Thanks

Krish

Hi

It can work but you will have to put in some additional valves to allow fluid to flow back into your pump cylinders. The system you propose is like a very early car braking system *( before Power assisted brakes). look up an old car braking system and you will see your system is the reverse of an old car. i.e. one master cylinder and four slaves and you have four masters and one slave.

Regards

Oliver Dunthorne

The diagram is confusing and/or incomplete. According to the orientation of the check valves, fluid can go from the SCs to the MC, but not back.

Hi All,

I apologise for the oversimplified picture earlier. Perhaps this one makes sense.

Thanks

Krish

With only check valves your system will NOT work.If at start of stroke you have a load on main cylinder the fluid will choose the lowest resistance path in your case the fluid will go directly to reservoir. At least this return valve has to be controlled.

Hi Nick Name,

I agree with your observation. I intend to use some mechanical means to close the directional valve connected to MC1 during stroke ( T0 to T1) and open it during return( T1 to T0).

Unfortunately I cant seem to figure out a hydraulic/mechanical way to bring the MC1 piston back to T0 position (reciprocate).

Let me try to describe the sequence as I understand it:

Step 1: Pressure is applied to SC1 piston which transfers the hydraulic pressure to MC1 and the MC1 piston move from T0 towards T1.

Step 2: Pressure is removed from SC1 and the spring loaded SC1 piston returns back to normal position creating a vacuum in its cylinder. This makes the hydraulic fluid to flow from the tank back into the SC1 cylinder.

Step 3: Pressure is applied to SC2 piston which transfers the hydraulic pressure to MC1 and the MC1 piston move further towards T1.

Step 4: Pressure is removed from SC2 and the spring loaded SC2 piston returns back to normal position creating a vacuum in its cylinder. This makes the hydraulic fluid to flow from the tank back into the SC2 cylinder.

Step 5: Pressure is applied to SC3 piston which transfers the hydraulic pressure to MC1 and the MC1 piston move to T1.

Step 6: Pressure is removed from SC3 and the spring loaded SC3 piston returns back to normal position creating a vacuum in its cylinder. This makes the hydraulic fluid to flow from the tank back into the SC3 cylinder.

Step 7: Since the piston position of MC1 is now at T1, I need it to reset to position T0. -- How can I achieve this action ?

ps: I understand I need to open the valve connected to MC1 for the return stroke and know how to achieve that. So this operation can be ignored.

Thanks

Krish

Hi Experts,

Please find below an updated diagram and process sequence based on various suggestions and inputs. Please advise if this will work?

Let me try to describe the sequence as I understand it:

Step 1: Pressure is applied to Slave Cylinder - SC1 piston which transfers the hydraulic pressure to Master Cylinder- MC1 and the MC1 piston move from T0 towards T1.

Step 2: Pressure is removed from SC1 and the spring loaded SC1 piston returns back to normal position creating a vacuum in its cylinder. This makes the hydraulic fluid to flow from the Reservoir back into the SC1 cylinder.

Step 3: Pressure is next applied to SC2 piston which transfers the hydraulic pressure to MC1 and the MC1 piston move further towards T1.

Step 4: Pressure is removed from SC2 and the spring loaded SC2 piston returns back to normal position creating a vacuum in its cylinder. This makes the hydraulic fluid to flow from the reservoir back into the SC2 cylinder.

Step 5: Pressure is next applied to SC3 piston which transfers the hydraulic pressure to MC1 and the MC1 piston moves to T1.

Step 6: Pressure is removed from SC3 and the spring loaded SC3 piston returns back to normal position creating a vacuum in its cylinder. This makes the hydraulic fluid to flow from the reservoir back into the SC3 cylinder.

Step 7: Since the piston position of MC1 is now at T1 and no pressure is being applied from any of the slave cylinders, the spring loaded MC1 piston returns back to T0. The relief valve is now opened to enable the fluid to return back to the reservoir due to the return spring action.

can you please advise if this system work in a reciprocating fashion ?

Thanks

Krish

This diagram is much clearer. The combination (check plus whatever feature) valve from the MC back to the reservoir needs more detail about what brings it into play (and keeps it out of play until then).

Hi Tornado,

Thanks for taking the time to review the design, its really appreciated. I need to work more on the relief valve connected to MC1. However hypothetically speaking, if it was to be assumed that the relief valve is closed during MC1 piston travel from T0 to T1 and relief valve is opened during MC1 piston travel from T1 to T0, will this design work?

I am considering an electro/mechanical way to control the relief valve but it needs more work.

Thanks again.

Krish

Hi

It will work but the springs in the check valves will have to be very light or no springs at all i.e mount them vertically. The relief valve will have to be the seated variety so as not to leak and presumably you will back off the relief valve when you want your master cylinder to return to base. You will have to be careful with seal selection as friction here can easily make spring return type actions very tricky.

Regards

Oliver Dunthorne

Durabla check valves are available with very low crack pressures. They are made by DFT, located in Exton, PA. They also have a variety of configurations.

www.dft-valves.com

Perhaps these might assist in the hydraulic circuit. I have used them in the chemical industry from vacuum breakers up to hydraulic systems. They have several unique bodies that lend themselves to many not often thought of solutions.

Good Luck, Old Salt

Hi Old Salt, Thats excellent information. Thank you. Krish

Hi Folks,

I have modified the circuit slightly to include dual master cylinders to counter the problem of un-intended pressure during return stroke of the master cylinder piston. By using a 4Way 2 Position direction control valve, I could achieve better results by reducing the idle time while the piston is returning back to normal T0 position. I am referring to 4/2 WAY AUTOMATIC DIRECTIONAL VALVES PKV on page 17 of http://www.poclain-hydraulics.com/_upload/ressources/media/pdf/A35758S.pdf. Please advise on the revised design below.