The purpose of lowering brake valves, also known as overcenter valves, is to prevent pulling loads on hydraulic cylinders or hydraulic motors from leading in an uncontrolled manner. The consumers are preloaded on the outlet side via the adjustable pressure valve. If necessary, this preload is released via an internal control bore, so that controlled movement is possible. The valves must always be set for the respective application. If the pressure at D1 exceeds the preload pressure of the non-return valve, the flow is released from D1 to U1. If the load pressure at U1 rises above the set value, the pressure relief valve opens and releases the flow from U1 to D1. If the load pressure at D2-U2 exceeds the set value, the pressure setting of the DBV is reduced proportionally to the specified load ratio until the pressure relief valve opens and releases the flow from U1 to D1. The DBV's spring chamber is relieved towards port D1.

Back pressure at D1 adds to the presetting of the pressure relief valve in all functions. To keep this effect as low as possible,

the connections of the upstream directional control valve should be relieved to the tank in the center position. The control line is hydraulically damped for greater stability at all volume flows and pressures.

The setting value of the DBV should be at least 1.3 times the maximum expected load pressure.

Schemes: