| 摘要 |
845,907. Hydraulic pit props. WIEMANN, E. W., [trading as MASCHINENFABRIK E. WIEMANN]. May 3, 1957 [May 3, 1956], No. 14262/57. Class 20(2) [Also in Group XXIX] In a hydraulic telescopic pit prop having a non-turn valve 4 allowing fluid to flow from the reservoir 1 to the pressure chamber 2 when the prop is extended by hand, the excess pressure relief valve 12 is adjustably and removably mounted in a plug cock 7 which is adapted to release fluid from the prop pressure chamber by a pipe 5 and a passage 10 to the reservoir to withdraw the prop. The cock 7 is operated by a key 16 and a quick screw thread 8. The relief valve comprises a spring-pressed ball valve held in position by a screw plug 121. Additional fluid may be pumped into the pressure chamber by means of a pipe 5<SP>1</SP>. |
