Winding – tensioning – or guiding – Convolute winding of material – With particular material guide or guard
Reexamination Certificate
2000-07-12
2003-01-21
Rivera, William A. (Department: 3653)
Winding, tensioning, or guiding
Convolute winding of material
With particular material guide or guard
C242S615400
Reexamination Certificate
active
06508431
ABSTRACT:
FIELD OF THE INVENTION
The present invention broadly concerns read/write electronic devices wherein a tape is used for recording or retrieving data. Specifically, the present invention concerns guides that facilitate packing of tape onto a take-up hub. The guide according to the present invention may be used with such electronic device or incorporated into tape cartridges. The device is particularly directed to prevent misregistration of the tape that is caused by air entrainment.
BACKGROUND OF THE INVENTION
Tape media are used to store data in a compact and accessible manner. Typically, this has been accomplished by winding the elongated strip of tape onto a reel. Typically, such reels are constructed to have a central hub that has annular flanges and a width slightly greater than the width of the tape. It is also known to use flangeless hubs in winding tape media. In either case, the hub is rotated about a central winding axis, and the length of tape is wrapped circumferentially around the hub. Such winding results in a tape pack as successive layers of tape build in a radial direction. The edges of the tape generally define a pair of oppositely disposed surfaces generally along planes that are perpendicular to the winding axis; the width of the tape pack is thus defined by the distance between these two planes. The flanges of a flanged reel are intended to protect the tape pack.
Storage reels of tape, whether flanged or flangeless (for example as used in cartridges) may be placed on the machine during use. The length of the tape is then passed through the machine so that information may be placed on the tape or retrieved therefrom. During this process, the length of tape is transferred onto a take-up reel or hub that is either a part of the machine itself, included within the cartridge or that is mounted and demounted from such machine. After being transported through the machine, the tape may be rewound onto the storage reel and removed from the machine.
In the beginning, the speeds associated with the transfer of tape between the storage reel and the take-up reel were relatively slow. The registration of the edges of the tape layers to form the opposite surfaces of the tape pack was not especially critical. Often, the edges of consecutive layers of the tape might be slightly off-set from one another or “stagger-wrapped”. Such was the case for both magnetic recording tape and tapes used, for example, in the motion picture industry (where a series of photographic images are placed consecutively on the tape medium).
In more recent times, the speed of wrapping or winding a tape onto either the storage reel or the take-up reel has increased dramatically. This is especially true in the electronic information storage arena wherein magnetic tape, or “film” or optical tape is used to store data, both for on-line usage as well as for archival purposes. In such electronic devices, a magnetic coil is used as a transducer to imprint data magnetically on a moving band of magnetic film; thereafter, when the film is advanced across the transducer, the data may be accessed. The ability to write data rapidly onto a film and the accessibility of data to be read from the film is a function of two variables: (1) the density of storage; and (2) the speed at which the tape medium may be transported across and accurately written/read by the transducer.
As was explained in my earlier U.S. Pat. No. 5,777,823, issued Jul. 7, 1998, it is important that the lateral edge of the tape moving in a transport direction be properly registered along a reference plane, called the datum, so that the data may be accurately input and retrieved from the tape medium. Support of the tape during transport is therefore critical, and typically employs guide rollers, air bearing and the like as is known in the art.
As tape transport speeds have increased, a problem has evolved which is interchangeably called “scatterwind” or “stagger-wrap”. Where tape is wound at high speed onto a hub, the tape entrains air. That is, air within the boundary of air adjacent to the tape moves into the tape pack and becomes entrapped between the advancing layer and those layers already on the tape pack. Some of this converging wedge of air is laterally displaced at the “nip” which is the point of tangency between the film pack and the incoming (or outgoing) layer of tape. Despite this displacement, a significant portion of the air is nonetheless trapped between the layers of the film pack such that the radial outward layers of the tape pack float slightly with respect to one another because they are separated by the spiral-air bearing created by the self-pressurized air film.
When the tape pack is subsequently brought to rest, the spiral-air bearing is ejected so as to decrease the pack's radius until all adjacent tape layers have come into direct contact. As this occurs, the layers may shift laterally with respect to one another resulting in a tape pack that has a significant amount of stagger wrap. Indeed, at the present time, there can be as much as 0.010 to 0.040 (about 0.25 mm to 1.0 mm) stagger between adjacent tape edges.
Stagger-wrap presents a problem to the industry where the alignment of the lateral edge of the tape is critical with the read/write transducer. If a tape pack has a significant amount of stagger wrap, the perturbation of this stagger wrap propagates through the advancing tape layer as it is played off of the reel or hub. This causes potential error in either reading or writing the data. Therefore, it is desirable to eliminate the misregistration of the layers forming the tape pack by guiding the registration of the incoming tape layer as it winds onto the hub.
As should be appreciated, when tape is wound between a take-up reel and a storage reel, it is necessarily under a physical tension “T”. The force required to displace a tape of length “L” through a misregistration “d” is given by equation: F=Td/L. By maximizing the length an minimizing misregistration, forces on the tape will be minimal subjecting the tape to the smallest and gentlest guiding force.
Others have recognized the air entrainment problem of high speed winding, and attempts have been made to address this problem. A general discussion of the air entrainment issue is discussed, for example, in M. B. Keshaven and J. A. Wickert, “Transient Discharge of Entrained Air from Wound Roll”,
Transactions of the ASME
, Vol. 65, 804-805 (December 1988) and in M. B. Keshaven and J. A. Wickert, “Air Entrainment During Study-State Web Winding”,
Transactions of the ASME
, Vol. 64, pages 916-917 (December 1997).
In U.S. Pat. No. 6,045,086 to Jeans, issued Apr. 4, 2000, a background discussion is set forth which describes various techniques employed in an attempt to reduce the stagger wrap or scatterwind. As explained in the '086 Patent, previous attempts at neatly packing a film onto a film pack include the use of self-packing glass reels, liner sheets, magnetic forces and mechanical forces. In the first Keshaven et al article noted above, the use of packing or “lay-on rollers” or drive belts that preload the tape against the roll have been used. However, those solutions can deform the tape. Moreover, the fragility of the thinner recording media and next-generation systems may effectively preclude the use of such mechanical means to reduce the thickness of the entrained air film.
Of the techniques noted above, self-packing glass reels are precision tape reels wherein the flanges are formed of glass. The flanges are slightly radially converging so that the decreased spacing of the flanges constrains lateral motion of the tape. These glass reels are high priced and require precise alignment or other guide elements in the tape path. In addition, the use of such self-packing glass reels do not eliminate the inertia of the flanged reels during acceleration and deceleration of the tape take-up and storage reels.
Magnetic winding devices rely on magnetic fields to align the film. This works only on magnetic films and is not possible to use to optical fi
Gegick Rebecca A.
Henson Michael R.
Martin Timothy J.
Rivera William A.
Segway Systems, LLC
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