Abstract: A pressure limiting valve has a piston sliding inside a piston bore in a piston guide. A valve spring and a spring plate move in a spring sleeve which has an adjusting screw at an end opposite the spring plate. The spring plate has flow-through openings. The piston extends into a blind bore in the spring plate. The piston guide, which forms the bottom of the spring chamber, has a funnel-shaped recess which extends to the inside wall of the spring sleeve. The spring plate support surface for the valve spring is below the top of the piston.

Abstract: The present invention relates to an adjustable support element for use in underground mining or tunnel construction, particularly for securing mining cavities at the longwall face and headway. The invention is a single use prop made of inner and outer telescopable tubes which can be filled with a hardenable building material core. The tubes have drainage boreholes for draining excess water from a liquid filling material pumped within the tubes after the prop has been braced between the roof and floor of the mines. Plural bands connected between the outer and inner tubes enable the telescopic movement of the tubes.