Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
2001-11-29
2004-02-10
Watko, Julie Anne (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head accessory
C360S231000
Reexamination Certificate
active
06690542
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a dual module magnetic record/reproduce head assembly, in particular to such an assembly that is capable of a read while write (RWW) operation, and to a technique for constructing such a head assembly.
BACKGROUND
The subject matter discussed herein generally relates to magnetic tape drives and, more particularly, to a magnetic tape head and techniques for assembly thereof, wherein the tape head assembly has multiple transducer heads which together form a predetermined overall contour, for multi-channel, high speed read-while-write type recording. As a general matter, a magnetic tape drive includes a head assembly, which carries at least a pair of transducers for reading information from and writing information to a magnetic tape as the tape passes over the assembly. The head assembly is positioned between a pair of guide rollers, which guide the tape over the head assembly. The head assembly is offset from the guide rollers during operations, to cause the tape to wrap onto the head.
Modern magnetic tape recorders utilize a read while write (RWW) capability to store data on the tape and to confirm that the writing of data was error free. A read-while-writing head assembly includes a write head in-line with a contiguous read head. The gap of the read head is closely spaced to the gap of the write head, with the read head positioned downstream of the write head in the direction of tape motion during the writing operation. The recorder continually reads “just recorded” data throughout the write operation, to check correctness of the data at a time while the original data is still available in temporary storage in the recording system. The “just recorded” data is read and checked against the original data, and appropriate action is taken upon detection of error. Many modern tape systems also support bi-directional writing to the tape. As such, the systems require that the head elements support the RWW operation for both directions of tape travel.
The heads in these assemblies are carefully contoured to achieve desired degrees of wrapping of the tape around the head assembly, as the tape contacts and passes over the head assembly. The transducers are fabricated on a ferrite or other ceramic substrate using thin film wafer technology.
For example, U.S. Pat. No. 5,034,838 to Brock et al. discloses a bi-directional magnetic head assembly consisting of two write heads arranged on opposite sides of one read head, along the line of bi-directional movement of the tape. Each inductive write head consists of two abutting segments of a refractory non-magnetic material, with a gap line formed along the abutment (perpendicular to tape travel). The magnetoresistive read head consists of two half sections with magnetoresistive transducing elements located in the gap between those sections. In this assembly, the central read head is curved and has slots on either side of its transducing region for skiving of entrained air and debris from the tape before the tape engages the transducing elements of the read head from either direction of tape travel. Each write head has a single slot outboard of the respective transducing gap for skiving entrained air and debris.
U.S. Pat. No. 5,953,184 to Barber et al. discloses a three-head assembly with a common surface contour. The assembly from this Patent includes an interior tape head module having a magnetic gap for the thin film transducers, with transverse slots on each side of the gap to eliminate air and debris as the tape moves in either direction over the module. The assembly also includes two exterior tape head modules, one on each side of the interior module. Each exterior module has a magnetic gap containing the appropriate thin film transducer elements and transverse slots on each side of the gap.
U.S. Pat. No. 5,237,476 to Bischoff et al. discloses a technique for forming a thin film tape head assembly. The patented method involves depositing thin film transducers on a ceramic wafer or substrate, which is then divided into head bars. Each head bar has one or more of the thin film transducers on its face. End sections and a cover bar are joined to the head bar to form a head bar subassembly. A flexible cable or electrical pins between the end sections enable electrical connection between the transducers in the head and external circuitry. The patent also suggests joining a number of these head bar subassemblies in parallel (perpendicular to the travel of the tape), to form a multigap thin film tape head for multiple read/write operations.
The trends in development of magnetic tape drives involve ever-increasing demands for the density of data stored on the tape as well as ever-increasing requirements for speed. With these trends, it is reasonable to expect that the tape head assembly must be re-designed if it can not function adequately at newly required higher speeds and/or higher densities. To avoid the need to re-design the tape head, particularly the contour thereof, there is a need for a tape head assembly that can operate properly at current speeds and can reasonably be expected to continue to function properly at higher speeds in next-generation tape drives. Stated another way, it is desirable for a tape head assembly to operate over a wide range of tape speeds.
As shown by the cited examples, there have been many different designs for the tape heads of digital data storage type tape drives. In some applications, it may be acceptable to dispose of the tape drive and thus the head after a working life of about three years. However, there are applications where the life expectancy of the drive is projected to be much longer, hence there is a need for a head assembly design that has low wear during protracted use and therefore a long life expectancy.
Another trend relates to expectations of decreasing costs. The costs of computer equipment and other electronic devices have continually spiraled downward for almost two decades. To continue to meet the demand for ever better tape drives at ever lower costs, there is a need for a design of a tape head assembly and an attendant manufacturing technique that reduces costs yet yields a high percentage of products with increased performance capabilities.
The use of a tape head assembly in a cartridge type system, particularly for a single real tape cartridge drive also imposes certain special requirements on the tape head. For example, in the single real design, there is a substantial difference in tension on the tape between initial withdrawal of tape from the reel and that required near the end of the tape. As a result, the head assembly must function properly over a wide range of tape tensions, with attendant differences in wrap and contact pressure.
A tape head assembly also should have a relatively high tolerance to differences in wrap angle of the tape about the assembly. To maintain a tight angle tolerance, the components of the drive must be built to very tight tolerances making the drive excessively expensive. If the wrap angle tolerance is relatively wide, the tolerances of other drive components are not as strict, and those components can be manufactured using less expensive techniques.
SUMMARY OF THE INVENTION
The inventive concepts meet the above noted needs for the structure and assembly of heads for read-while-writing (RWW) type magnetic tape systems. A tape head assembly, in accord with the aspects of the present invention, comprises two modules bonded together, for example, in a back-to-back arrangement. However, the initial phase of the manufacturing technique produces a single unit containing elements of both modules, for example, in a head-face to head-face arrangement. Transducer elements for both modules may be formed initially on different halves of a single substrate that is common to both modules.
The modules are initially gapped in pair, in order to produce a good reference surface, which insures that the head will meet tight azimuth and gap distance tolerances in a low cost assembly process. The unit is then machined to
McDermott & Will & Emery
Seagate Removable Storage Solutions LLC
Watko Julie Anne
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