| 摘要 |
<p>1478529 Boring earth &c B J HUGHES INC 22 Nov 1974 [14 Jan 1974] 50760/74 Heading E1F A well drilling rig has racker apparatus comprising an upper racker 54 and a lower racker 55, the lower racker being movable upwardly and downwardly along the mast 24 by means of a powered cable drum 83. The lower racker has rollers (80), Fig. 4 (not shown), which engage in vertical guide rails 79, and the racker is held in its upper position by means of retractable stops 91. Both rackers are provided with horizontal racker arms 61, 76 having heads (63, 78), Fig. 2 (not shown), for engaging a well pipe, and the arms are movable towards and away from the centre of the mast and also laterally.</p> |
