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Hydraulic Cushioning Valve Configuration

Hydraulic Cushioning Valve Configuration

(OP)
Hello All. New here, and new to hydraulic circuit design. I would like some feedback on the cushioning valve configuration shown in the attached schematic. I'm working on a system with hydraulics that are used to lift large mixing bowls which sometimes are abruptly stopped (safety mat trigger). In all the reading and examples of how to use cushioning valves, I have yet to see a circuit as the one on this machine. Is it correct? Is it doing something I don't understand?

Note: The cushion valves themselves appear to be drawn incorrectly, in that the pressure lines are not dashed, and the valve is shown such that flow through it is the normal position.

RE: Hydraulic Cushioning Valve Configuration

The drawing is wrong...very wrong actually.

The cushion valves are also known as counterbalance valves. They should be drawn as relief valves that are opened by upstream pressure at the cylinder.

The check valve should allow free oil flow to the cylinder and should block the oil flow coming from the cylinder.

RE: Hydraulic Cushioning Valve Configuration

Also, placing two cylinders in parallel (hydraulically) and using one speed control valve is not a good practice unless there is a mechanical linkage between the cylinders to keep them synchronized.

RE: Hydraulic Cushioning Valve Configuration

Bowl2 doesn't look right. What is it supposed to do? It isn't relieving to anywhere.

Why not move into the 2100s? Relief valves will not anticipate the impact and limit the impact forces.

Even if 100% retract signal is applied to a servo valve when the pressure or force reaches the set point the valve will NOT respond in time.

We control 4 axis cushions. Each axis has a servo quality valve. There is NO WAY relief valves are going to limit the impact. The relief valves do not respond quickly enough. Neither will servo valves UNLESS you anticipate the impact.

Limiting the impact force is similar to a base ball catcher moving his mitt backwards in anticipation of impact. On top of that the impacts can be simulated and therefore controlled.

We have done research on controlling impacts. We can gather positions, velocities, pressures and forces at 1 millisecond or faster. Without this information one is designing in a vacuum.

Peter Nachtwey
Delta Computer Systems
http://www.deltamotion.com
http://forum.deltamotion.com/

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