Hi all! I've been working on a design for a mining conveyor that requires it to fold up in a way I haven't done before and I was wondering if anyone here know how to get the functionality below working. So I have 2 sets of hydraulic rams, one set to hold the conveyor up and to change it's angle, and another set to fold it and unfold it. However the lifting rams are to be connected to the folding section of the conveyor. Which means that while the conveyor is being folded or unfolded the lift rams must float, and vice versa. The lift rams need to naturally extend, and retract during the folding operation. When the lift rams are being operated in either direction the fold rams must float (to allow partial unfolding using lift rams) When the lift rams are not being operated they must hold the load, preferably with over centre valves, unless fold rams are being operated, in which case they must float again. Fold rams do not need to be locked in neutral position as the lift rams will support the weigh, however if possible it would be great if both sets of rams could be locked out in neutral position. As the conveyor folds 180°, there will be runaway load effect on both sets of rams, since the load will go over the pivot point so over centre valve or at least a needle valve should be integrated in the circuit somewhere to prevent choppy movement or even worse vacuum and cavitation. I've drawn several circuits to try and work this out but it just doesn't seem like it would work. Has anyone ever encountered a circuit like this, or have any suggestions on how I would go about making this work? Perhaps there's some easy way of doing it using some component that I didn't think of. Thanks a lot it advance!
Unless you add pilot control blocks to port oil or allow the porting of oil at different demand points it will not function. Can change that to linkage as on tractor loaders for bucket leveling control but all will get is a leveling not a curling or unfurling. Have seen multi function control handles to get a desired action but are extremely complex as well troublesome, a joystick/pistol grip control as on a electrical man basket truck would allow multi functions with minimal effort.
Take a look at the tip section of this crusher unit. The tip folds beneath the main conveyor. It has a linkage and lever at the break point. They've also incorporated a take up cylinder that keeps a touch of tension on the belt so that it doesn't fully slack. This is a KPI FT2650 track mounted jaw. It doesn't elevate up or down as you are trying to do but perhaps you could glean an idea or thought from its design. Reading your description again, perhaps ditch the second set of cylinders for cables on an arc so that as the conveyor frame is raised or lowered, the cables would act on a fixed point against a guided arc or shive to achieve your desired articulation. As DMiller pointed out, if you want to "hold" you're gonna need a pilot to release source of lesser oil pressure maybe even a restricted flow from the "B" port to the release port of the load holding valve.
look at the attached valve catalog. They offer 4 way 4 POSITION WITH FLOAT configurations.
I don't understand why you need to float the lift cylinders when trying to fold or unfold the conveyor? It is a two circuit function requiring two valves. The operator can move the lift cylinders anyway necessary to facilitate the fold and unfold circuit. If it has to be automatic without operator intervention then you are looking at some sort of digital processor with an algorithm to control flows and convertor movement.
Check how the linkage is arranged in Wirtgens mills also. They also have a folding conveyor with linkage. A lot of systems anymore are way to complicated for what they are to do. KISS (Keep it simple stupid)