To restore a hammer bank to be in a normal speed as much as possible in the event of a rapid increase in load on the hammer bank to prevent a fall in printing speed and to reduce frequency of occurrence of malfunctions of a printer in a linear motor shuttle mechanism having an urging means operating in the inverting time of the hammer bank, thereby improving reliability of an apparatus.

In a term of a constant speed of the hammer bank, the minimum speed at a time when the speed is abnormally lowered, is detected, and then a current for restoring the speed depending on the speed is applied to the hammer bank.