Original Publication Date: 1989-Dec-31
Included in the Prior Art Database: 2004-Apr-05
Xerox Disclosure Journal
A single component development process may use an insulative, non-magnetic toner which is metered and charged on a donor roll by the reverse rotation of a biased charging rod. The roll and rod are spaced apart by a toner layer formed on the donor roll. The toner metering and charging is dependent on the contact force between the charging rod and the donor roll. This requires that the uniformity of the nip pressure along the length of the nip must be controlled in order to obtain uniform metering and charging. Hereinbefore, the charging rod was made from an electroformed nickel sleeve mounted on a foam core. The nickel provided wear resistance and electrical conductivity while the foam core provided a uniform loading along the length of the nip. The nickel sleeve was thin so that slight variations in donor straightness were compensated for by flexing of the nickel sleeve. In order to reduce costs and simplify manufacturing, this rod was replaced by a small diameter solid rod supported in a segmented, spring comb holder. Each comb finger applies pressure independently of the other fingers so as to furnish the nip force load. A small diameter rod must still be capable of conforming to variations in the straightness of the donor roll. This requires very tight tolerances on the straightness of both the rod and donor roll to prevent nip variations. A more flexible rod reduces the straightness tolerance requirements. A rod formed by spirally wrapping wire or ribbon and grinding to achieve a smooth surface finish represents a design with improved rod flexibility.