Metal deforming – Process – Deforming stacked blanks
Reexamination Certificate
2000-01-19
2001-05-08
Larson, Lowell A. (Department: 3725)
Metal deforming
Process
Deforming stacked blanks
C148S604000
Reexamination Certificate
active
06227029
ABSTRACT:
1. Field of the Invention
This invention relates to belt-driven data tape cartridges, and more particularly to such a cartridge assembled on a base plate that is specifically flattened to assure precision alignment of components for accurate registration and improved operation within an associated tape drive.
2. Background of the Invention
Belt-driven data tape cartridges commonly include a pair of tape hubs and a plurality of tape guides positioned along a tape path between tape hubs for guiding the tape along the path between the hubs. The tape passes an access port at which a tape transducer makes operational contact with the tape for recording data to and reading data from one or more of a plurality of recording tracks on the tape as the tape moves bidirectionally between hubs. To increase total data storage within a cartridge, additional length and width of tape may be provided, and additional recording tracks may be established along the tape of increased width. However, practical limitations on the maximum length and width of tape within the cartridge are imposed by the maximum external dimensions of the cartridge that can be received in associated conventional tape drives. Accordingly, additional recording tracks are established across the width of the tape and along the length thereof by the tape transducer that operatively interacts with the tape in order to increase the total amount of data that can be stored in such a tape cartridge. However, as track widths and the spacings between tracks decrease, higher precision and registration accuracy are required between tape in the cartridge and the transducer in the tape drive in order to assure highly reliable writing and reading of data on the tape. Various servo-controlled positioning schemes are known for dynamically positioning the transducer with respect to a recording track in order to adjust to anomalies in width of tape and orientation of tape relative to the transducer as the tape moves along the tape path between the hubs and past the transducer.
In contemporary tape drives for data tape cartridges, resiliently-biased detent mechanisms that can be overridden by force manually applied to insert or remove the cartridge commonly retain a cartridge in proper orientation relative to the tape drive in order to assure that the transducer and the tape tracks properly align. However, one source of misalignment of transducer and tape tracks is distortion of the base plate upon which operational components of a tape cartridge are mounted. Since the base plate provides planar reference for perpendicular orientations of the tape guides and of the pins upon which rotating hubs and belt rollers are mounted, and since the base plate also provides elevational reference for the height at which a recording track is located along the length of tape, slight distortions of the base plate from flat contribute major misalignment problems that are not compensated by the resiliently-biased detent mechanism which retains the tape cartridge in operational position within the tape drive.
In addition, tight control of transverse tape tension in higher packing density cartridges is important for reliable read and write operation. Transverse tape tension refers to the difference in tape tension against the tape transducer head from the top edge of the tape to the bottom edge of the tape. This is an effect of the difference in path length of the tape between the top and bottom edges of the tape.
If all hub pins and guide pins were perfectly parallel, there would be no difference in path length between top and bottom edges of the tape and therefore no differences in transverse tape tension. Differences occur from the non-perpendicularity of the pin insertions into the base plate, and is a function of the alignment of the various pin presses on the assembly line which can be carefully controlled and adjusted. Another source of different transverse tape tension is the curvature of the base plate itself.
If all the pin presses were set for zero deviation from the perpendicular at the point of insertion, but the base plate itself is curved, the pins would not be parallel. Thus the flatness of the base plate must be improved in order to meet transverse tape tension requirements.
Conventional base plates for tape cartridges use stippled upper and lower surfaces to stress-relieve the base plate material and allow it to remain flatter. Conventional base plates tend to have a natural curvature since they are stamped from coiled raw material and are straightened in the manufacturing process. The straightening process does not completely remove the memory of the material of its previously coiled condition.
Base plates for industry-standard tape cartridges currently are stamped from rollstock of aluminum material grade type # 5052-H34 that is approximately 0.080″ thick and that is unrolled for stamping and punching to establish outer dimensions and interior apertures for press-fitted pins and guides. For high-volume production, the same die that stamps out individual base plates from the unrolled sheet aluminum also punches apertures and presses the surfaces of the individual base plates to stipple or emboss the surfaces and flatten the base plate. However, multiple strips of rollstock may be cut from across the width of a master roll of the aluminum material, and individual base plates stamped from strips that were oriented near the edges of the master roll exhibit greater waviness out of planarity than is exhibited by individual base plates stamped from strips that were oriented near the center of the master roll. Wide variations in flatness of base plates are thus exhibited throughout a population of base plates stamped from various orientations relative to the master rollstock, where such variations are inadequately corrected by stippling or embossing and momentary pressing of the surfaces of the individual base plates.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, base plates for supporting the components of a belt-driven tape cartridge are stamped from sheet stock of aluminum to selected dimensions that are smaller than the dimensions of the sheet stock. The population of base plates thus produced from various orientations along the sheet stock are generally flattened during initial processing and apertures for insertion therein of the tape guides and pins are punched in normal orientation to major faces of the base plate at selected coordinates thereon that are unique for one orientation of a base plate. The base plates are then stacked together in mixed orientations for heat treatment under surface pressure applied to the stacked base plates in direction normal to the major faces thereof. In this way, grain structure of the aluminum base plate is reoriented to minimize residual stress and assure flatness without curl or warp between boundary edges and across comers of the generally rectangular base plate.
REFERENCES:
patent: 60-99431 (1985-05-01), None
patent: 61-219425 (1986-09-01), None
Fenwick & West LLP
Larson Lowell A.
Verbatim Corporation
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