Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
2001-03-28
2003-07-01
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head accessory
Reexamination Certificate
active
06587305
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, in general, to magnetic tape head assemblies for use in conjunction with magnetic contact recording media, and more particularly to a tape head with a transducer support assembly with protective edges, i.e., at the leading and trailing edges, adjacent the core to create an increased height or radius adjacent the core and read/write gap to enhance air removal and to provide wear protection for the softer core materials during high speed operations with a number of recording media or tape having varying stiffness.
2. Relevant Background
Magnetic head assemblies typically contain one or more raised strips or supports that have surfaces over which the magnetic recording media, e.g., tape, passes. Embedded in each support surface is a transducer which may be a recording transducer (i.e. recording or writing head) for writing information (i.e., bits of data) onto the media or a reproducing transducer (i.e., reproducing or reading head) for reading information from the media. An embedded recording transducer produces a magnetic field in the vicinity of a small gap in the core of the recording transducer that causes information to be stored on the magnetic media as it streams across the support surface. In contrast, a reproducing transducer detects a magnetic field near the surface of the magnetic media in the vicinity of a small gap as the media streams over the support surface.
There is typically some microscopic separation between the gap of the transducer core and the recording media. During operation, this separation must be tightly monitored and controlled to avoid or minimize “spacing loss.” The separation reduces the magnetic field coupling between the recording transducer and the media during writing and between the media and the reproducing transducer during reading. The magnetic field coupling decreases exponentially both with respect to increases in the separation between the media and the support and with respect to increases in the recording density. The amount of media area required to store a bit of data is a factor in determining recording density and as less media area is required to store a bit of data, the recording density increases. Thus, while a higher, more easily obtainable amount of head-to-media separation may be acceptable at low recording densities, the growing demand for higher recording densities has led to the need for tighter control over the head-to-media separation that can be tolerated to obtain useful levels of magnetic coupling.
To control spacing loss, a tension is applied to the tape as the tape passes at a wrap angle around a support surface and an adjacent transducer core surface each having a height and a width. Due to this tension, the tape exerts a pressure against the support surface, and if the support surface and core surface have uniform widths and heights, the pressure is substantially uniform along a longitudinal axis of the support. The pressure is essentially proportional to the tension and the wrap angle and inversely proportional to the support width.
In some tape head assembly designs, the pressure is intentionally increased to control spacing loss. For example, the pressure can be increased by increasing the tension in the tape, by modifying the wrap angle of the tape on the support surface, and/or by modifying the width of the support surface. However, increased pressure is accompanied by negative consequences including reduced tape life, increased possibility of tape damage and data loss, and support and core surface wear leading to a shortened head life. Moreover, increased pressure can result in uneven wear along the support surface, which can be particularly troublesome between regions of the support and the transducer core. As can be appreciated, increased and uneven wear rates become more serious problems as operational speeds for magnetic head assemblies are increased.
Operational problems with head wear and uneven wear have recently grown with the use of magnetic media having varying stiffness. For example, a magnetic head assembly may be used to read and write to a magnetic tape with a given stiffness that causes the magnetic tape to have a corresponding natural radius and contours. The support surfaces and core typically will wear to fit better this radius and natural contours of the tape. When the magnetic head assembly is then used with a magnetic tape having a different stiffness, e.g., a higher stiffness tape, a larger and sometimes unacceptable separation distance may initially exist until again the magnetic media is worn or broken in to match the new tape stiffness. Hence, there is a need for a magnetic head assembly that address the need for wear control that is also useful for magnetic media of varying stiffness.
Several magnetic head assembly designs have been developed in attempt to address these wear problems. In many tape head assembly designs, the pressure at the core is increased to enhance magnetic coupling by providing an elongated support assembly in which the width of the core and adjacent surfaces is less than the width of the adjacent elongated support surfaces. This smaller width makes the pressure applied non-uniform along the longitudinal axis of the support with higher pressure being applied at the core area and providing a better contact area. Unfortunately, this head design often results in higher wear rates at the core area that may lead to uneven wear within the support assembly. In some cases, higher core wear rates and pressures have been addressed with the use of wear resistant materials for the core center and/or in the adjacent supporting surfaces that are either parallel to the travel path of the media over the core or on all sides of the core.
In a different design approach, the support area near the core is made wider than the adjacent elongated support surfaces to obtain a softer or lower pressure mating of core and magnetic media. Wider core area designs are described in detail in U.S. Pat. Nos. 5,426,551 and 5,475,533 to Saliba, which are both incorporated herein by reference. The wider support surface near the core results in less pressure being applied at the core which is beneficial in controlling uneven wear. The wear rate is further controlled by providing wear surfaces of glass or other nonmagnetic material adjacent the magnetic ferrite core positioned parallel to the travel path of magnetic media. The wear rate is self-regulated to be relatively uniform along the longitudinal axis of the support assembly because the pressure is less than on the elongated support surfaces that are fabricated of a more wear resistant material. While addressing some industry problems, these wider core area devices tend to function well initially but then also develop problems of uneven wear on support surfaces and of core wear as the entire support assembly experiences wear. Additionally, the height of the core and adjacent wear surfaces typically are selected for a particular media and media thickness and experience wear that makes the device better suited for continued use with that media rather than for several media with varying stiffnesses.
Additionally, air flowing under the magnetic media during higher speed operations can cause spacing losses, and airflow needs to be addressed during magnetic head assembly design. During operation, air is moved within the magnetic head assembly as the magnetic media rapidly advances across the surfaces of the assembly facing and supporting the magnetic media, such as the support surface and the core. Spacing losses can develop when the flowing air passes between the core and read/write gap and the magnetic media. In the narrower core area devices, air tends to be channeled over the core because it first strikes the wider adjoining support surfaces and then is forced into the narrower core area. The wider core area devices provide better airflow control with the air first striking the wider core area and being channeled away towards the adjacent, narrower support area
Cao Allen
Morrison & Foerster / LLP
Quantum Corporation
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