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 from D1 to U1 is released. 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 rises above the set value, the pressure setting of the DBV is reduced proportionally to the specified control ratio until the pressure relief valve opens and releases the flow from U1 to D1. The DBV's spring chamber is relieved towards the atmosphere. This means that a possible back pressure at D1 does not affect either the open control behavior or the presetting of the DBV.

The control line is hydraulically damped for greater stability at all volume flows and pressures. The setting value of the pressure cartridge should be at least 1.3 times the maximum expected load pressure.

Pressure setting must be at least 1.3 times higher than the load pressure. Both opening pressure and control pressure are independent of any back pressure.

Normally used when the ports A+B of the upstream directional control valve are blocked in neutral position. In addition, the working ports of the directional control valve must be fitted with shock and suction valves.

Schemes: