Point by point positioning apparatus

Claim 1

A positioning apparatus for positioning a movable assembly, comprising: a. a general control motor for moving said movable assembly, b. a stepping motor for moving said movable assembly, c. a stationary linear detection instrument including a series of transverse conductive lamellae insulated from one another, each adjacent pair of lamellae defining a different predetermined position along the path of travel of the movable assembly, d. means movable with the movable assembly and cooperable with said lamellae for successively short circuiting adjacent pairs of said lamellae, e. detection circuit means for producing an output signal only when said movable means (d) short circuts an adjacent pair of lamellae corresponding to a predetermined position of said movable assembly, f. additional detection means responsive to the reversal of direction of movement of said movable assembly for producing an output signal, and g. logic circuit means between said detection circuit means and said motors, said logic circuit means including: I. means for actuating said general control motor to move said movable assembly into a predetermined position and then past that position, Ii. means responsive to the output signal from said detection circuit means (e) for braking said general control motor and hence said movable assembly, and Iii. means responsive to said output signal from said additional detection means (f) for deactuating said general control motor and for actuating said stepping motor to move said movable assembly, in a direction opposite to the direction it was moved by said general control motor, back toward said predetermined position.