| 摘要 |
Two axially telescoping tubular form housing units, with the top one held in contact with the roof by an adjacent pressure medium, make up a mechanism for erecting a concrete or similar pillar-type support in a mine. Each unit comprises two open-ended half shells. Those for the bottom one, at least, are foldable about a swivel axis parallel to their common longitudinal axis. The top unit is set under the influence of resilient pressure media pref. helical spring, supported on a pit prop clamped between roof and floor. This is inexpensive, and promptly effective, and readily adaptable to varying distances between roof and floor. |
