Abstract: A print wire solenoid device including a disc type plunger-restoring spring which consists of a continuous annular peripheral portion and spoke portions extending radially inwardly therefrom jointly to define a central opening for fitting engagement with the plunger. The plunger and the stationary core or stem members defining a solenoid gap, therebetween are both conically formed to minimize leakage of magnetic flux, thereby substantially increasing the effective flux density and hence the force of attraction. The disc spring, which is neither fixedly secured at any point to the plunger nor to the other adjacent components, is free from any stress concentration in operation and thus not only enables high speed printing operation with an increased length of stroke but facilitates fabrication of the device in combination with the conical formation of the plunger and stem members, which facilitates reduction in size and weight of the devices as well as in power consumption.

Abstract: A step motor is employed as a source of power for transverse feed of the printing head assembly with a combination of a slitted rotary disc secured to the motor output shaft and a stationary detector unit provided to control the motor operation and the dot-printing head operation in precisely timed relation to each other. The rotary disc is also slotted to serve the purpose of defining for the printing head assembly a print starting position spaced a definite distance to the right from its rest position. The printer structure, including a minimum of movable component parts, is capable of forming characters without any lack of "dot" and is minimized in power consumption and noise particularly in idling operation.