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.