Abstract: An improved print hammer actuator for dot matrix printers employs a substantially closed loop magnetic path including a resilient magnetic hammer, a number of such hammers being aligned in a hammer bank assembly which is shuttled back and forth along a printing line at a high rate of speed, while the hammers are individually actuated by energizing coils which overcome a permanent magnetic field normally maintaining the hammers in retracted position. Heat conducting elements are mounted in heat transfer relationship with each of the different ones of the coils in the hammer bank, and high surface area fins on the elements extend into an air flow directed across one side of the hammer bank. For this purpose the hammer bank assembly is configured to define an interior air channel along its length and includes a fixed top cover and spaced apart circuit board forming part of a plenum and directing air frontwardly from a rear mounted fan.

Abstract: An electromagnet is disclosed. The electromagnet has a winding that is wet wound with an epoxy material filled with grains of a material having a high coefficient of thermal-conductivity. The entire winding is empotted dry in a similar epoxy having grains of the said material. Fins are connected to the outside of the dry empotment for carrying away heat transferred to the fins from the coil.

Abstract: Individual wires in a winding are formed as polygons having contacting faces and noncontacting faces. Contacting faces of adjacent wires are positively engaged, while the noncontacting faces of adjacent wires form the periphery of openings that extend through the winding. Insulation may be removed from the noncontacting faces to facilitate cooling.