Why would these hydraulic cylinders have 3 large connections?

Question

I am trying to work out how a recently acquired Arburg 220-90-350 from 1982 works so that I can build a new control system and get it working. It's a direct clamping machine with no toggle.
The injection side is quite simple, just 3 motors or cylinders each controlled by a separate valve.
The clamp and ejector side has me confused though, there is a directional valve controlling each cylinder (simple enough) but each cylinder has a 3rd line the same size as the others connected to another single valve labelled 'high pressure'. So to summarise, 2 hydraulic cylinders each with 3 hoses, 3 directional control valves controlling the 2 cylinders.
I can't begin to draw a schematic without further disassembling the machine so I am hoping someone can give me some reasons why a hydraulic cylinder would have 3 hoses of equal size, with 1 on each cylinder connected to the same valve.
Edit:
On further investigation, I can confirm that non of the 3 hoses are connected together, i.e. there is not two in parallel.

Terry Gould · Accepted Answer

So it turns out that the ejector cylinder is just a standard double-acting cylinder with 2 hoses, the remaining 4 hoses are all used for the clamping cylinder.
Two of the large hoses do retract and return at low pressure, the two remaining hoses one large and one small do the high pressure clamping.
This is standard for a 2 platten direct clamping machine. The platen closes under low pressure and when it is closed the high pressure gives it the final clamping force.

Why would these hydraulic cylinders have 3 large connections?

One Answer

Add your own answers!

Ask a Question