High-capacity pressure limiting valve

Pressure limiting valve for protecting hydraulic units, especially protecting the hydraulic face support of underground operations against rock bursts or other overloads, comprising a control piston that is movable inside an internal bore in a valve casing against a force of a valve spring, wherein said control piston blocks off an adjustment screw bore associated with a spring chamber and cooperates with a valve piston with blind bore and radial bores, which is guided in a movable manner in an expanded large bore that merges into a compensation chamber and is sealed via sealing rings, and which, when subjected to pressure, connects the cross-bores serving as discharge bores with the large bore by driving over the sealing rings, characterized in that

• the control piston (4) and the valve piston (20) are separate units, that the valve piston is movable against a spring (33) supported on the control piston side (32) and has a through-bore (31) with a smaller diameter than the blind bore (8) of the control piston (4), and wherein the sealing rings (27, 29) associated with the valve piston are constructed as plastic rings and are rectangular and very hard, and that are preloaded when they are installed.