Impact Force Compensation For Voltage Variations In The Hammer Firing Pulse In Impact Printer
Original Publication Date: 1979-Oct-01
Included in the Prior Art Database: 2005-Feb-20
The present apparatus relates to a modification of the printer hammer mechanism described in U.S. Patent 4,030,591. In such impact printer apparatus, the hammer which applies the impact is driven by a solenoid which is energized by a solenoid driving pulse from a hammer drive circuit. In this conventional apparatus, the solenoid driving pulse is applied by turning current on for a period of time, e.g., T(1), and then the current is turned off. However, the total power is subject to risetime fluctuations due to variations in the voltage supply. In order to minimize variations in the printer impact force, the point at which the pulse timing is initiated is not a fixed time but rather determined by the time when the current reaches a selected level, i.e., the current level is sensed and this triggers the pulse timing.