Description
Dual overcenter valves typically have three ports: a load port, a rod port, and a pilot port. The load port is connected to the hydraulic cylinder that is moving the load. The rod port is connected to the opposite side of the cylinder. The pilot port is connected to a pressure source, such as the hydraulic pump.
When the directional control valve is in the neutral position, the dual overcenter valve closes both the load port and the rod port. This prevents the load from moving. When the directional control valve is moved to the lift position, the load port opens and the rod port remains closed. This allows the cylinder to extend and lift the load.
When the directional control valve is moved to the lower position, the load port remains closed and the rod port opens. This allows the cylinder to retract and lower the load. However, the dual overcenter valve also meters the flow of oil out of the rod port. This controls the speed of descent of the load and prevents it from running away.
The pilot port is used to control the opening and closing of the dual overcenter valve. When pressure is applied to the pilot port, the valve opens. This allows the load port or the rod port to open, depending on the position of the directional control valve. When the pilot pressure is released, the valve closes.
