Improvements in gyroscopic directional devices and borehole surveying instruments incorporating the same

Claim 1

A DIRECTIONAL DEVICE COMPRISING AN OUTER FRAME, A FIRST GIMBAL JOURNALLED FOR ROTATION IN THE OUTER FRAME ABOUT A FIRST AXIS, A SECOND GIMBAL JOURNALLED ON THE FIRST GIMBAL FOR ROTATION ABOUT A SECOND AXIS NORMAL TO THE FIRST AXIS, A GYRO WHEEL JOURNALLED FOR ROTATION IN THE SECOND GIMBAL ABOUT A THIRD AXIS NORMAL TO THE SECOND AXIS, ELECTRIC MOTOR MEANS FOR ROTATING THE WHEEL AT HIGH SPEED, DIRECTION INDICATING MEANS ROTATING WITH THE FIRST GIMBAL, GRAVITY SWITCH MEANS ON THE SECOND GIMBAL FOR DETECTING DEFLECTION OF THE THIRD AXIS FROM ITS STABLE HORIZONTAL POSITION, MEANS RESPONSIVE TO THE SWITCH MEANS FOR APPLYING A TORQUE TO THE FIRST GIMBAL ABOUT THE FIRST AXIS IN A DIRECTION CALCULATED TO CAUSE PRECESSION OF THE THIRD AXIS BACK TO THE STABLE POSITION, AND MEANS FOR PROVIDING A PLURALITY OF CURRENT PATHS BETWEEN THE FIRST AND SECOND GIMBAL SUCH MEANS INCLUDING GROOVED GUIDES ON THE FIRST GIMBAL WITH THE GROOVES FACING THE SECOND GIMBAL, GROOVED GUIDES ON THE SECOND GIMBAL WITH THE LATTER GROOVES CONCENTRIC AND CO-PLANAR WITH THE GROOVES ON THE