Printer having improved hammerbank airflow

Abstract

An improved hammerbank in a dot matrix line printer has two different sets of staggered apertures therein along the length thereof for drawing pressurized air at the outside of the hammerbank therein to provide turbulent, high velocity cooling air in the region below the magnetic coils of the magnetic hammer actuators. The cooling air is confined to passage over the magnetic coils by enlarged flanges on the coil bobbins which form an air dam. The air dam discourages escape of the cooling air through spaces between the hammer springs. Magnetic interaction between adjacent magnetic hammer actuators is minimized due to the absence of common magnetic materials extending therebetween, except for the permanent magnets which hold the hammer springs in the retracted position. The permanent magnets are common to a plurality of the magnetic hammer actuators and by physically extending therebetween serve to prevent substantial leakage flux from occurring. The hammerbank is mounted for reciprocating motion by a single, intergrally formed, hollow shaft which extends through the entire length of the hammerbank and beyond the opposite ends thereof. The hammer springs are mounted by screws driven into endless screw holes which terminate at the cooling apertures within the hammerbank so as to accommodate relatively long screws and at the same time expel debris that might otherwise accumulate within the screw holes. The upper portions of a cover assembly at the front of the hammerbank are held in fixed relation by magnetic clip assemblies mounted thereon and having permanent magnets attached thereto in a manner which permits precision grinding of the clip assemblies.