Disengageable nut and screw arrangement

Claim 1

In combination with a precision instrument, an adjusting mechanism comprising an externally threaded fine adjusting screw rotatable about its longitudinal axis, a nut having at least a partially threaded bore interengaging with said screw through which an axial force may be transmitted to said nut upon rotation of said screw, said nut including a smooth bore having a diameter larger than the diameter of said screw extending therethrough at an angle to said partially threaded bore and having an axis which intersects the axis of said partially threaded bore at substantially the midpoint thereof, means for rotating said nut about a tilting axis extending through said point of intersection and perpendicular to the axis of said screw for selectively aligning said screw with either said partially threaded bore or said smooth bore, whereby said nut may be slid axially over said screw when said smooth bore is aligned with said nut and said nut may be translated relative to said screw upon rotation thereof when said partially threaded bore is aligned with said screw, the resultant of the force transmitted by said screw to said nut upon rotation of said screw passing through said tilting axis.