Process and apparatus using ultra-filtration in the production of can shells

Abstract

In the production of drawn and ironed seamless metal cans an elongated sheet, for example, of tin-plated steel or aluminum, is lubricated and fed to a blanking and cupping press which cuts the sheet and forms it into shallow cups. The cups are fed to a series of ironing dies which thin the sidewalls of the cups and produce tall, smooth shells. While in the sidewall ironer the cups, shells and dies are flooded with an oil-in-water emulsion which acts as a lubricant and coolant. The can shells are trimmed to obtain a uniform height, and washed. The lubricant-coolant is re-circulated to and from the wall ironer by the coolant system which contains tanks, pumps, conventional plate-frame filter, chiller, etc. to remove heat and contaminants. Can shells emerging from the ironing process carry a relatively large amount of coolant as "drag out". Some of the dragged out coolant is dripped into the waste pit while the rest is removed in the can-washing operation. The addition of a prerinse preferably between the ironing and trimming operations removes most of the "drag out". The effluent from the pre-rinse is then dewatered by use of an ultra-filtration pressure membrane system to concentrate it back to "use" concentration (as an emulsion) for direct return to the coolant system for re-use in the ironing process. The water removed, the permeate, is re-used in the prerinse station.

Dependencies are inferred from the claim text.