| 摘要 |
A downhole tool (10) comprises a slip member (32) pivotable about a pivot axis between retracted and extended configurations to engage a bore wall, wherein the slip member (32) defines an actuation surface (44) and a brace surface (46). The tool (10) further includes a wedge member (34) defining a wedge surface (42), wherein the wedge member (34) and slip member (32) are configured to move relative to each other such that interengagement between the wedge surface (42) and the actuation surface (44) causes said slip member (32) to pivot. When the slip member (32) is in the extended configuration the actuation surface (44) is in engagement with the wedge surface (42) of the wedge member (34) and the brace surface (46) is in engagement with a support surface (66) formed on the tool (10). Further, a ratchet mechanism (16), which may form part of the downhole tool (10), comprises a reference member (18) comprising a surface ratchet profile, a ratchet mandrel sleeve (90) arranged coaxially with the reference member (18) and defining a plurality of circumferentially distributed windows (96), and a circumferential ratchet assembly (102) arranged generally coaxially with the ratchet mandrel sleeve (90) such that the ratchet mandrel sleeve (90) is interposed between the circumferential ratchet assembly (102) and the reference member (18). The circumferential ratchet assembly (102) comprises a plurality of circumferentially distributed ratchet members (106) or projections each comprising a surface ratchet profile and arranged to extend through a respective window (96) in the ratchet mandrel (90) to permit relative engagement between the ratchet profiles of the reference member (18) and the ratchet members (106). The ratchet profiles permit movement of the ratchet mandrel sleeve (90) and ratchet assembly (102) relative to the reference member (18) in a first direction, and resist relative motion in an opposite second direction. |
