The present invention relates generally to a housing for a two spool tape or data cartridge for magnetic recording tape of the type used in computers and the like, and is particularly concerned with an improved fastener mechanism or system for coupling or connecting the opposed lower and upper walls of the housing together.
Typical magnetic tape cartridges include an outer housing and various internal components including tape, a pair of rotatable spools carrying the tape, and a drive mechanism. The housing usually comprises a metallic baseplate and an opposing cover member of plastic material. Where the baseplate and cover member are rigidly secured together, warpage of the housing can occur as a result of the different rates of thermal expansion of the materials forming the baseplate and cover. This warpage results in some deflection of the tape transport path, which is unacceptable in view of the very high track densities on current magnetic data tapes, requiring a high degree of precision in the tape transport.
In U.S. Pat. No. 4,571,789 of Morioka, a fastener mechanism for connecting the baseplate to the cover in a manner allowing for some degree of different relative thermal expansion is described. The mechanism comprises a single rigid fastener between the baseplate and cover which is located on the mid-line of the cartridge, and a series of snap fasteners between the baseplate and cover, one each adjacent each corner of the cartridge. The snap fasteners each have a pair of spring arms separated by a slot which can absorb some of the differential expansion between the baseplate and cover by allowing the arms to move towards and away from each other. However, this arrangement only allows relative motion between the baseplate and cover in one lateral direction, parallel to the front of the baseplate, since the spring arms can only move towards and away from each other in this direction, as permitted by the slot. The snap fasteners are actually quite stiff in the front to rear direction. Additionally, the snap fasteners do not provide a secure connection between the baseplate and cover and thus allow some potential for separation of the baseplate from the cover, especially along the front edge of the cartridge where it contacts the drive mechanism and thus encounters relatively large forces.