Electrostatic fountain developer

#This invention relates to the developing of electrostatic images such as is performed in xerography and ionography, and in particular, to a new and improved fountain for delivering liquid toner to a receptor for developing an electrostatic image into a visible image.

#In a typical system, an electrostatic image of varying charge density is produced on a receptor, such as a selenium plate or a sheet of dielectric plastic. Toner particles are deposited on the receptor, with the toner density being proportional to the electrostatic field density normal to the receptor. The toner is then fixed in place, as by heating, and the image is ready for viewing. In some systems, dry toner is used with the charged receptor being exposed to a cloud of the toner particles. In other systems, liquid toner is used with the charged receptor exposed to a liquid having the toner particles suspended therein.

#The present invention provides an improved fountain for delivering the liquid toner to the receptor and is particularly useful with systems wherein the latent electrostatic charge density is small thereby requiring the use of a sensitive toner (low charge per particle) and developing system.

#FIG. 1 is a diagramatic illustration of an electrostatic image developer with a fountain incorporating the presently preferred embodiment of the invention;

#FIG. 2 is an enlarged end view of the fountain of FIG. 1;

#FIG. 3 is a side view of the fountain of FIG. 2 with the cover plate removed;

#FIG. 1 illustrates a typical electrostatic image developer with a receptor 10 carried on a drum 11 and held in place by vacuum. The drum is positioned above a tank 12 of liquid toner 13. A fountain 14 is supported on a pipe 15 mounted in a pump housing 16. A pump in the pump housing delivers liquid toner to the fountain through the pipe 15. It is preferred to have the fountain pivotted between a lowered position shown in dashed lines and a raised working position shown in solid lines to prevent toner from drying on the various surfaces of the fountain.

#The fountain includes a body 20 with cover plate 21 attached by screws 22'. A liquid toner receptacle is provided in the body and includes a sump 22 and a flow passage 23. Liquid toner is delivered to the pipe 15 into the sump 22 and flows upward through the flow passage 23 into a pool at the upper end of the fountain.

#The pool is formed by end members 26, 27, a side member 28, and the upper end of the plate 21 which serves as another side member. The bottom of the pool is formed by a bottom member 31, an electrode 32, and another bottom member 33 which may be formed integrally with the side member 28.