This invention relates to information storage systems and in particular to an information storage system having a receptacle wherein a recording cartridge containing a sheet of flexible information storage media is inserted for reading and writing information on the media.
In recording or reading information on a moving information storage media, such as a magnetic recording disc, relative motion between a magnetic head transducer used for reading and writing information and the storage media on which information is written on and read from is required. The relative velocity between the head and media interface may be, for example, 550 IPS for video and high density digital applications. To achieve maximum performance, an interface of intimate contact is provided between the head and the media surface without destruction or excessive wear of the magnetic flux responsive coating on the surface.
As contact pressure between the head and media is increased to improve performance, both media and head wear are increased. The problem is particularly severe in video applications and compounded with the medias utilized for storing single video frames on separate tracks of a magnetic disc wherein one track at a time is continuously in contact with the head to provide a continuous stationary display of a single frame. In only five minutes of playtime revolving at 3,600 RPM, for example, a track on the disc is scraped about 18,000 times by the head; the by-products are so hard and abrasive that the same materials are commonly used as lapping compounds.
To prevent failure caused by contact between the head and disc, lubricated surfaces and/or air film separations have been used. However, any separation between the head and disc caused by such lubricating fluid or air film imposes a loss of signal and hence performance. A head/disc separation equal to one wave length could cause about 54.6 db loss in the output of the replay head. Since it is desired to record wave lengths that approach 1.75 microns, the playback head voltage is reduced to 50% by only 0.19 microns of separation. On the other hand, as discussed above, reduction of separation to meet desired performance would cause the interface to be destroyed within a few seconds.
Prior art solutions to the head-to-disc interface problem have generally been of two types: flying heads in conjunction with rigid hard-surface discs and heads having large surface areas buried in soft flexible "floppy" discs. Flying head discs are very expensive and require complicated and expensive recording/playback systems. A flexible or so-called "floppy" disc reduces the handling and cost problem incurred in the flying head, rigid-disc system. Some recording/read heads for "floppy" discs are relatively large to provide an interface comprised of a large contoured head buried in the soft flexible media. The large record/read head surface area distributes the force per unit area to reduce media wear and separation loss. As the media is moved past the head, however, air collects between the head and disc surface to form an air film. The thickness of this air film is a function of head and media finishes, media stiffness, head-media penetration, head size, head surface contour, viscosity of the air and disc-head relative velocity. Because of these restraints, most flexible or "floppy" disc applications are limited to slow speed, low bandwidth digital computer applications or voice recording systems.
In U.S. Pat. No. 4,175,274, means for biasing a magnetic recording disc toward the recording head by aerodynamic pressure is described and claimed. The specific embodiment described therein is a flexible spring member affixed to the inside cover of a recording cartridge. The present invention relates to an improved embodiment for biasing the disc toward the head and maintaining an intimate head-to-disc interface.
In recording systems known in the art the head is moved vertically as well as horizontally with respect to the media. To prevent damage to the media when the head is repositioned, the head is first moved vertically away from the media, then moved horizontally to the desired track location and finally moved vertically toward the media to assume its proper position for system operation. This procedure necessitates the use of a solenoid, servosystem or other means for moving the head both horizontally and vertically, thus adding to the number of components and the expense required to operate the system.
Many information storage systems are adaptable for receiving portable cartridges containing the storage media therein. Such cartridges may include a tab, seal or other means which, when removed by the user, opens an electrical circuit in the information storage system to prevent information stored on the media from being erased. This allows the user to protect the information, but has the disadvantage of precluding subsequent erasure of the information on the media and use of the cartridge to record new information unless the tab or seal is somehow replaced.