| 摘要 |
A down hole surveying tool (10) for directional surveying of boreholes. The tool (10) comprises a body (11) which accommodates a two-axis gyroscope (13) and a two-axis accelerometer (15). The gyroscope (13) and accelerometer (15) are rigidly fixed with respect to each other to provide a composite sensor device (17). The sensor device (17) is supported in a rotary mount (31) for rotation about an indexing axis (4). The sensor device (17) can be indexed about the indexing axis between two indexing positions which are 180 degrees apart. An indexing mechanism (70) is provided for selectively indexing the sensor device (17) about the indexing axis (4). The indexing mechanism (70) comprises a drive portion (71) and a driven portion (72) adapted for selective interaction to impart indexing motion to the sensor device (17). The driven portion (72) is movable into and out of engagement with the drive portion (71) upon rotation of the rotary mount (31) about a pitch axis (1) using a pitch drive mechanism (51). |
