Impact printing apparatus and method using reluctance switching and a closed loop drive system

Abstract

An electromagnet and a permanent magnet are arranged in parallel between first and second pole pieces having a metallic spring tine coupled to the first pole piece and disposed to be attracted to the second pole piece by the magnetic field of the permanent magnet. A sensing coil is positioned to sense magnetic flux changes resulting from changes in position of the metallic spring tine. In operation the spring tine is displaced to the second pole piece and captured at a home position by field energy from the permanent magnet. When there is a demand for printing, the electromagnet is energized in a first polarity such that its reluctance to the field of the permanent magnet is minimized and the flux from the permanent magnet is attracted to pass through the core of the electromagnet thereby nullifying the traction between the spring tine and the second pole piece and the spring tine is released. Potential energy stored in the tine by the displacement of the tine is transformed to kinetic energy and the tine moves swiftly to effect a print impact. Following impact, the electromagnet is energized in a second polarity such that its reluctance to the field of the permanent magnet is of the spring tine. Flux movements detected by the sensing coil are utilized in a closed loop system to regulate amplitude and polarity of the field of the electromagnet for home, release and capture cycles of the apparatus.

Dependencies are inferred from the claim text.