Patent ID: 6064559
Filing Date: 2000-05-16
Classification: G01D

Abstract:
A sealed servo-type variable tuning capacitor comprising a hermetically sealed canister; a set of fixed plates within said canister; a set of movable plates meshed with the fixed plates and axially movable within the canister; a shaft affixed to said movable plates and moves axially with respect to said canister; a nut affixed non-rotatably on said shaft and having a female thread; a rotatable threaded lead screw fitted into said nut; means for controllably rotating said lead screw to move said nut, and thereby said movable plates, over a travel defined between a home position and at least one other position; and the improvement which comprises an optical indexing arrangement for detecting whether said nut and said movable plates are in said home position, including optical transmitter means generating an optical beam, optical receiver means oriented to receive said optical beam, said beam traveling on a path at a predetermined axial position within the travel of said nut; and flag means disposed on said nut to block said optical beam on said path when said nut is in home position, but being out of said path and permitting said optical beam to pass from said transmitter means to said receiver means when said nut is out of said home position.