Lockable motor drive

摘要

This invention provides a motor drive assembly for rotatably positioning and locking a drive shaft suitable for use with a measurement-while-drilling (MWD) downhole assembly for use in drilling boreholes which utilizes gyroscopes, magnetometers and accelerometers for determining the borehole inclination and azimuth during the drilling of the borehole. The motor drive assembly can rotate the gyroscope and other sensors on the tool to one of a plurality of preselected positions and optionally lock the sensors.