1. Field of the Invention
The present invention relates generally to computer data storage devices such as tape reel cartridges. In particular, the present invention relates to an apparatus for rotary stabilization and drive engagement of a tape reel housed within a tape reel cartridge.
2. Description of the Prior Art
Computer systems presently use a variety of devices to store processed data. One such storage device is a cartridge with encodable magnetic tape therein. The tape passes over a sensory head which encodes data onto the tape in a magnetically recognizable pattern. The sensory head may also be used for data retrieval which includes decoding the magnetic pattern and reading the data from the tape. This encodable magnetic tape is used in VHS videocassettes and high fidelity audio cassettes with respective tape drive systems. Typically, the cassette is engaged by a tape drive system to allow indexing of the tape across the sensory head to encode and retrieve data magnetically stored on the tape.
One type of tape cassette consists of two reels laterally spaced from one another with magnetic tape connected to and circumferentially wound about each reel. A drive mechanism engages one or both of the reels to rotate the reels thereby transferring the tape from reel to reel. As the tape is wound from one reel to the other, it passes over the sensory head for encoding or retrieval of data.
A second type of tape cassette consists of a single cassette reel design. A loose end of the tape engages a reel or tape winding structure that is part of the tape drive mechanism. The tape winding structure pulls the tape from the single cassette reel, over a sensory head for encoding and retrieval of data. The tape may be wound on an external reel, or may be fed back onto the cassette's reel as an "endless loop" of tape.
In either cassette type, the reels are typically enclosed in a tape reel housing and each reel has a circular platter connected to a hub about which the tape is wound. The hub is typically engageable by a drive mechanism to cause rotation of the hub and platter. By controlling rotation of the hub and platter, the tape is either wound onto or unwound from the hub.
One such cassette of the single reel type is used for computers with 1/2 inch magnetic tape. The hub on the reel in this cassette is mounted on the housing on a rotational axis perpendicular to the platter by a center pivot between the hub and the housing. The center pivot includes a self-enclosed radial commercial ball bearing with its outer race affixed to the hub and its inner race affixed to a stem mounted to the tape reel housing. The circular platter is engageable with reel locks mounted on the tape reel housing which can be moved into engagement with the edge of the circular platter to constrain rotation of the reel.
A coil spring is used to urge the hub against an external tape cassette drive mechanism, thereby maintaining the hub in alignment for proper rotation within the housing, and in appropriate alignment for engagement with the drive mechanism. However, the use of a coil spring as the sole mechanical connector between the hub and housing provides a less stable arrangement than is desired, since the spring may have a tendency to bend during rotation. Since the current bearing is essentially a radial load design and is being used to transmit a thrust load, the bending and vibration of the spring is transmitted through the bearing's outer race to the reel.
This direct influence of the dynamic forces from the spring on the reel can cause a variety of problems. One such problem is undesirable vibrations which can occur during rotation of the hub. The vibrations result because the coil spring reacts to varying loads which are placed on it as the hub and platter rotate. The reel tilts randomly in response to the vibrations that can lead to nonuniform tape winding about the hub. Poor tape winding may result in damage to the tape and possible data loss.
Another concern with the present tape reel cartridges involves the relative cost of the commercial self-enclosed ball bearing used in the center pivot of the hub. The self-enclosed bearing is disproportionately expensive relative to the other parts of the cartridge.
For these reasons, there is a need for an inexpensive tape reel cartridge bearing for the 1/2 inch computer tape cartridge that provides stable rotation and drive engagement of the tape reel and which is easy to assemble. Desireable characteristics for such a bearing include a stable center pivot and rotational axis for the tape reel so that spring bending and spring vibrations during tape reel rotation are minimized.