Abstract: A particulate image developer material mixing system for a reproduction apparatus, with a rotatably driven helical mixing coil in a developer material sump for mixing the developer material in the sump, and with a system for holding the rotatably driven helical mixing coil in the sump, and a system for anti-bridging of the developer material by agitating the developer material in the sump by agitating the mixing coil; including a smoothly rounded rod substantially extending inside of the helical mixing coil with a smoothly enlarged diameter end portion outwardly radiused to operatively intermediately engage the mixing coil so that as the helical mixing coil is rotatably driven at least one coil thereof is periodically partially detained and deformed on the smoothly enlarged diameter end portion and then periodically released automatically after a further rotation, so as to provide a periodic anti-bridging agitation of the developer materials, at a desired frequency, and the free end of the helical mixing coil

Abstract: An improved system for exchanging a developer unit of a copying or printing machine by moving the developer unit between a portable developer unit transporter cart or the like and the development station of the machine while the cart is docked in alignment therewith, the cart has a liftable development unit holder and a simple but effective foot pedal operated lifting system for automatically lifting it up to the same level as the development station in said machine, so that developer unit rails thereon are in accurate alignment with rails in the development station for easily moving a developer unit therebetween, irrespective of variations in the level of the cart and the machine due to floor or machine alignment differences. Also disclosed is a system of assisting the lateral alignment of the cart with the machine for docking, and safety interlock systems.