Closed loop mechanical development control system

An apparatus and method for developing an electrostatic latent image on an imaging member wherein a development nip is formed between a rotatably mounted cylindrical developer roll and the imaging member. The nip is initially supplied with a wedge shaped layer of developer material to develop the electrostatic latent image on the imaging member. Periodically at stated intervals the developer material is collected from the developer roll and development nip and the same measured amount of developer material is resupplied to the development nip. The apparatus includes a developer material supply means comprising a developer material hopper having a dispensing aperture at the bottommost portion thereof adjacent the developer roll, a movable dispensing slide in operative association with the developer material hopper, the slide having in succession a solid portion for sealing association with the aperture in the hopper, an aperture for dispensing association with the aperture in the hopper and the cleaning doctor blade for cleaning engagement with the developer roll to collect developer material in the pile as the slide is movable back and forth from sealing association with the hopper aperture and for cleaning the developer roll.