Feeder module with thickness detection

Abstract

A feeder module for feeding sheet inserts and having a thickness detector for measuring the thickness of inserts comprises: a gripper drum disc for transporting the inserts upon its periphery; a detector caliper assembly including a pivotable arm having a follower roller borne at one end and a magnet mounted at the other end, the arm being spring loaded with the follower roller against the periphery of the gripper drum disc; and, a stationary Hall sensor to measure relative displacement between the sensor and the magnet. As an insert is transported upon the periphery of the gripper drum disc, the insert is interposed between the periphery and the follower roller and the Hall sensor senses the consequent magnet displacement as a measure of the thickness of the insert. In one embodiment, an adjustable anvil having a peripheral surface is mounted on a face of the gripper drum disc. The anvil is pre-adjusted so that its peripheral surface is disposed at a constant radius from the axis of rotation of the disc. In another embodiment, signals provided by the Hall sensor in absence of inserts are stored as reference signals. Signals provided by the Hall sensor in the presence of an insert are compared with the corresponding stored reference signal to provide an accurate measure of insert thickness regardless of eccentricity of the gripper drum disc periphery.