| 摘要 |
The invention relates to a pressure-relief valve, in particular for hydraulic telescopic props and the like, which has in a piston bore of the valve housing a valve piston which can perform a stroke against the restoring force of a valve spring and is provided with an axial bore and with radial bores which branch off from the axial bore and, during opening of the valve, run over an O-ring sitting in an annular groove of the piston bore of the valve housing so that the pressure fluid can flow off via the radial bores and an outflow space arranged in the valve housing. According to the invention, the spring space having the valve spring is sealed off from the outflow space and is constantly connected to the pressure side of the valve via the continuous axial bore of the valve piston, the valve piston having a piston extension which plunges into the spring space in a sealed-off manner and on which the valve spring acts. In this way, the valve piston is constantly partly pressure-balanced so that a relatively weak valve spring can be used. According to a further feature of the invention, at least two groups of radial bores are provided on the valve piston, a separate O-ring in the piston bore being allocated to each of these groups, which run over the O-ring when the valve responds. In this way, a large fluid quantity per unit of time can be drawn off when the valve responds.
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