Print wire actuating device for a dot matrix printer

摘要

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.