CA2263783C - Method for poling a ceramic piezoelectric plate - Google Patents

Abstract

In the embodiments of the simplified ink jet head described in the specification, a carbon body is formed with ink passages, such as internal passages (19, 21, 25) extending through a carbon plate (26), pressure chambers (2) on one side of a carbon plate (26), flow-through passages (24) on the other side of the same plate and ink supply passages (19, 25), and a piezoelectric plate (23) is affixed to the pressure chamber side of the carbon plate by a thin layer of epoxy adhesive. The piezoelectric plate (23) may have a conductive coating on one side which is photo-etched to produce an electrode pattern corresponding to the pattern of the pressure chambers in the carbon plate. An orifice plate (13) may have specially profiled orifice openings (12) to assure axial projection of drops and may be affixed by a thin layer of epoxy adhesive to a carbon plate (26) having orifice passages (21) supplying ink from the pressure chambers (20) to the orifices (12). Since the carbon plate is conductive, it can be used, if desired, as an electrode on the opposite side of the piezoelectric plate (23) and, to assure grounding of the piezoelectric plate, a conductive epoxy adhesive may be used to bond the piezoelectric plate to the carbon plate. Moreover, since the carbon plate is porous, it can provide a communication path (76) between a vacuum source (77) and an air-permeable, ink-impermeable layer (75) on the ink passages to remove dissolved air from the ink in the passages. In one alternative embodiment, an ink jet head assembly contains two separate carbon pressure chamber plates, a carbon manifold plate and a carbon collar to retain the carbon plates in an assembly.

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for poling a ceramic piezoelectric plate comprising compressing a ceramic piezoelectric plate between electrode plates with a slightly conductive rubber sheet interposed between each electrode plate and the ceramic piezoelectric plate and applying an electric potential to the electrode plates to pole the piezoelectric plate, the slightly conductive rubber plates being effective to provide intimate electric contact with the piezoelectric plate while limiting the current available for arcing in the event of breakdown.

2. A method for poling a ceramic piezoelectric plate comprising applying one surface of a ceramic piezoelectric plate to a ground plate and applying electric charge from a corona discharge device to the opposite surface of the ceramic piezoelectric plate until the applied charge is sufficient to create a breakdown.

3. A method for poling a ceramic piezoelectric plate according to claim 1, including the steps of removing the electric potential from the electrode plates and again applying an electric potential to the electrode plates to minimize stresses in the ceramic piezoelectric plate.