| 摘要 |
1,152,382. Telescopic derrick masts. YOUNGSTOWN SHEET & TUBE CO. 1 June, 1966 [28 June, 1965], No. 24346/66. Heading E1F. A mast comprises at least two sections 104, 105 secured in extended position by latches 102a, 102b on section 104 outwardly urged by spring 111 when aligned with slots 101a, 101b. To disengage the latches, section 104 is raised from the position shown until retractors 121a, 121b, move the latches inwardly where they are held by spring-urged locks 113a, 113b, whereupon section 104 can be lowered. The locks are carried on a common shaft on section 104 actuated by a lever controlled by a trip block 131. The lever has a lostmotion connection with the shaft whereby on initial extension of the section the lever withdraws the locks to allow the latches to move outwards and, on further raising, the lever passes block 131 to allow the looks to engage the retracted latches but turns without moving the shaft when section 104 is then lowered. The sections are interconnected by various arrangements of pulleys and cables to a travelling block which is moved to extend or contract the mast. |
