| 摘要 |
A device of a derrick is described comprising lifting- and lowering equipment (20) for movement of a drill tring/pipe string (17) in axial direction in a derrick and gripping- and holding equipment </= <slips >/= 16, 18) , which are arranged at the upper and lower end of the lifting- and lowering equipment (20), to individually and in turn, grip and release, respectively, the string (17) in connection with lifting and lowering of same. The device is characterised in that the lifting- and lowering equipment is comprised of a single pressure-medium cylinder (20) with hollow (pipe-formed) piston rod (23), that the string (17) is arranged to run through the piston rod (23) and associated cylinder part (21) in an unhindered way and that the pressure-medium chamber (25) of the cylinder part (21, which is arranged to take up the associated piston (28) of the cylinder (20) and associated hollow piston rod (23), is limited in the cylinder part (21) between an outer wall (26) and an inner wall (27). The piston rod (23) is preferably rigidly rotating connected to the cylinder part (21).
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