Ink jet printing

Claim 1

Apparatus for forming images on a record member with droplets of ink, comprising: a. a record member; b. means for projecting a stream of ink toward the record member, said projecting means including an ink projecting member in the form of a capillary tube having two ends with an axis along which the ink is projected, a nozzle capping said capillary tube at one end, means for supplying ink to the capillary tube under pressure to cause a stream of the ink to be projected from the nozzle toward the record member, and a capillary tube mount to which the capillary tube is fixed at the end opposite said nozzle; c. a driving member which is joined to said ink projecting member, comprising a metal reed, a reed clamp located at the midsection of said capillary tube before the end of the reed to fix the metal reed in position, and means for inducing microscopic longitudinal vibrations of the joined metal reed and capillary tube, yoked to said metal reed between said capillary tube mount and said reed clamp, comprising an ultrasonic transducing means yoked to an end of said metal reed, away from said nozzle, including a metal paddle extension of said metal reed which is of the same thickness as the metal reed, but of greater width, and a piezoelectric ceramic element appended to the underside of the metal paddle extension and of considerably greater thickness than said metal paddle extension, with a potential difference being applied between said metal paddle extension and a lower surface of said piezoelectric ceramic element to cause a microscopic vibration of the element, a longitudinal component of which is transmitted through said metal paddle extension to said metal reed; d. means for inducing a macroscopic oscillation of the joined ink projecting member and driving member at a resonant frequency of the joined members, said oscillation being in a direction substantially transverse to the axis of the projecting means, whereby the stream of ink is projected within a plane of trajectory variation defined by the axis of the projecting means and the direction of oscillation; e. closed loop feedback means for ensuring that the joined projecting member and driving member oscillate at or near the resonant frequency of the driving member over time; f. means for electrostatically charging drops of ink at a point at which the stream breaks up into individual drops; g. means for controlling said charging means to form two charge groups having either a "deflection" or a "no deflection" charge on drops emerging from the projecting means during predetermined portions of the oscillation period; h. means for inducing the deflection of drops bearing a "deflection" charge in a direction substantially transverse to the plane of trajectory variation, while allowing the drops bearing a "no deflection" charge to remain on course; i. means for intercepting drops in one of the two charge groups after deflection of the drops bearing a "deflection" charge; and j. means for causing a relative movement of the record member in a direction substantially transverse to the plane of trajectory variation, whereby the drops of the nonintercepted charge group are deposited on the record member to form an image.