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Symmetrical Deflection Magnet Structure

IP.com Disclosure Number: IPCOM000081050D
Original Publication Date: 1974-Mar-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Dumke, WP: AUTHOR

Abstract

This is a deflection magnet structure for magnetic ink jet printing which has several improved performance characteristics. The conventional structure used has a core with a wedge-shape opening which produces a tangential magnetic field H(y) with a radial gradient partial derivative H(y) over partial derivative x. There are two important shortcomings of the field that are produced, however. First, this gradient is not really constant and may therefore result in a non-linear dependence of deflection on drive current. Second, in producing the gradient a large magnetic field is also produced. Any changes in this field while a droplet is traversing it will result in an altered exit velocity and a non-uniform rate of arrival of droplets at the medium to be printed.

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Symmetrical Deflection Magnet Structure

This is a deflection magnet structure for magnetic ink jet printing which has several improved performance characteristics. The conventional structure used has a core with a wedge-shape opening which produces a tangential magnetic field H(y) with a radial gradient partial derivative H(y) over partial derivative x. There are two important shortcomings of the field that are produced, however. First, this gradient is not really constant and may therefore result in a non-linear dependence of deflection on drive current. Second, in producing the gradient a large magnetic field is also produced. Any changes in this field while a droplet is traversing it will result in an altered exit velocity and a non-uniform rate of arrival of droplets at the medium to be printed.

An improved structure is shown in Fig. 1. The directions of the windings 10 are arranged so that the magnetic field contributions from the two halves 12, 14 of the structure are opposite in sign and cancel at the midpoint (dotted line) between the two structures. In Fig. 2 the central part of this structure is shown enlarged to show the field configuration in the gap of this structure.

When the pole pieces have a shape such that xy = constant over their surfaces then the solution for the scalar magnetic potential will be V(m) = axy. The magnetic field gradient in the gap will be

(Image Omitted)

and will be uniform over the gap (with the exception of its extremities)....