Roof-support system for mines

摘要

The invention relates to a roof-support system for a mine, in which the roof girder is kept in contact with the roof during the advance of the support in the direction of a conveyor by the props of the support being connected to a low-pressure fluid pipe which has a small bore. In order to prevent the build-up of a back pressure in the pipe which interferes with the advance of the support if the roof and the floor approach one another, a pressure-actuated valve is provided in the low-pressure-fluid supply circuit of the props. This valve normally connects the props to the low-pressure pipe. If a back pressure builds up in the props, this back pressure displaces the valve so that the props are connected to the normal return line until the pressure is removed, after which the valve moves into its normal position. <IMAGE>