Driver for boring bar for electric discharge machine

Claim 1

A rotary driver for a rotary borIng bar of an electric discharge boring machine, or the like, comprising: a boring bar drive head and a boring driven head having, respectively, a fixed longitudinal axis of rotation, and a longitudinal axis of rotation which may coincide in one position of adjustment with said fixed axis to be parallel to and shortly spaced from said fixed axis by variable distances in other positions of adjustment, said heads being positioned opposite to one another with their adjacent sides substantially in a plane perpendicular to said axes, said sides having confronting annular faces substantially in said plane rotatably adjustable relatively to one another, said drive head having a hollow drive stem concentric with said fixed axis of rotation thereof to receive, with clearance, a boring bar, one of said heads having a cylindrical eccentric bore extending inwardly therein, circumscribed by its said annular face, and having a center axis eccentric to said fixed axis by a predetermined offset distance, and the other of said heads having a circular eccentric projecting therefrom, circumscribed by its said annular face, and received in said bore with a light frictional but manually rotative fit, said eccentric having a center axis which is eccentric by said same offset distance from said fixed axis, means mounting a cylindrical boring bar on said driven head on an axis laterally offset from the center axis of said eccentric bore and eccentric by said offset distance, said last mentioned axis coinciding with said fixed axis in one position of rotation of said eccentric relative to the one of said heads that contains said eccentric bore, said eccentric bore terminating at its inner end in an annular shoulder, and there being a reduced bore extending from said shoulder and remainder of the way through said driver head for accommodation of said boring bar, a sealing ring between said annular faces, and a sealing ring between said shoulder and the inner end of said eccentric, said sealing rings excluding dielectric from the interior of the drive and driven heads.