Linear actuator for a memory storage apparatus

Abstract

A linear actuator comprises a pair of central poles symmetrically arranged parallel to the direction of motion of a carriage for transducers. Four permanent magnets are disposed around each central pole leaving predetermined gaps. Four ambient poles and one terminal pole surround the permanent magnets and each central pole. Two driving coils are slidably movable in the predetermined gaps therebetween. Upper and lower flat plate members support the driving coils so they may be fixed to the carriage. The central poles each have a rectangular cross-section, the permanent magnets surrounding the exterior four walls of the central poles leaving the predetermined gaps in which the driving coils are disposed. The ambient poles and terminal poles surround the central poles and form closed magnetic circuits. The flat plate members of the carriage are composed of ceramic material. The driving coils, arranged inside the predetermined gaps, are mounted at the ends of the flat plate members. According to the above construction, the driving coils are entirely applied for driving the carriage. Moreover, due to the decrease in the quantity of the windings of each driving coil, and the light weight of the flat plate members, the carriage is light in weight while the linear actuator provides powerful actuation forces and achieves fast data access times. Furthermore, the pair of magnetic circuits ae closed as that the linear actuator reduces leakage flux and magnetic noise to a minimum.