Rotating disk memories usually comprise one or more disks driven about a vertical axis. Each disk has a plurality of concentric tracks on one or both surfaces from which or to which signals are received or transmitted by means of reading and writing heads. A positioner moves the heads over the surface of the disk, generally radially with respect to the disk, and thereby locates a reading or writing head over a track as required.
Prior positioners comprise a drive unit coupled to a support and a carriage unit mounted on wheels that moves in ways on the support. These prior positioners are subject to two problems. One is wheel wear. Any wheel wear means the carriage can move off its normal line of travel. With spacings of less than 0.010 inch between track centers, any such deviation can cause positioning errors on the disk because the heads are themselves cantilevered on long arms extending from the carriage. The arms magnify any carriage deviation.
It is also difficult to align prior positioners. Whenever a carriage or drive unit is replaced, especially in the field, a technician must first combine the drive and carriage units as a subassembly and align them along a drive axis so the carriage and drive units move freely. Then this subassembly must be mounted and aligned to orientate the heads properly with respect to a disk.
Therefore, it is an object of this invention to provide a more reliable positioner which is less subject to wheel wear.
Another object of this invention is to provide a positioner which simplifies on-site replacement and alignment.