WO1999049464A1

WO1999049464A1 - A device to partially contact a magnetic recording head

Info

Publication number: WO1999049464A1
Application number: PCT/US1999/006439
Authority: WO
Inventors: Coen J. Warmenhoven; Gregory Leger; Hakan O. Hemdal; Patrick W. Lafferty
Original assignee: Plasmon Lms, Inc.
Priority date: 1998-03-26
Filing date: 1999-03-24
Publication date: 1999-09-30

Abstract

A tape drive for handling a magnetic tape comprises at least two magnetic heads, each head having magnetic surface. The magnetic surfaces define part of a tape path for a magnetic tape when mounted in the device. A moveable lifting mechanism has at least a first position and a second position. The tape path is altered when the mechanism is moved between the first and the second position. When the mechanism is in the first position, the tape path lies across all the magnetic surfaces of the heads. When the mechanism is in the second position, the tape path lies across less than all of the magnetic surfaces of the heads.

Description

A DEVICE TO PARTIALLY CONTACT A MAGNETIC RECORDING HEAD

BACKGROUND AND SUMMARY OF THE INVENTION This invention generally pertains to the field of magnetic tape recording and playback devices, generally referred to hereinafter as "data recorders." In particular, the invention relates to the interface between the magnetic tape and the recording and/or playback pickup surface (the "head" or "heads").

Data recorders and, in particular, the "tape drive" portions of such data recorders, are known in the art. Well known manufacturers of tape drives include Philips, IBM, H.P.,

Hitachi, Fujitsu, Exabyte, Storage Tek, Overland Data, etc. The "tape drive" is known in the art to refer to components of the data recorder that interfaces with and handles the magnetic tape, including reels, heads, bearings and guides.

The magnetic tape used in tape drives is often packaged in a cartridge supplied by a manufacturer, such as the CrO₂ tape in the 3480/3490 cartridge. Such a cartridge typically interfaces with a spindle in the tape drive, thus allowing tape to be payed out and/or taken up during recording and/or playback.

Data recorders and tape drives typically have separate magnetic heads for writing and reading a magnetic tape. The read and write heads are often mounted together such that the surfaces of the heads that read or write the magnetic tape all form an approximately contiguous surface over which the tape passes. Today, common configurations of read and write heads mounted together include a "Write-Read-Write" or a "Read-Write-Read" configuration. (In the former, a read head is mounted between two write heads, while in the latter a write head is mounted between two read heads.)

Such configurations of heads allow both reading and writing of the tape passing over it. For example, in the "Read-Write-Read" ("RWR") configuration, the data recorder can read the tape immediately after writing in, thus verifying if the data is written correctly, without any errors. Because of the symmetry of the RWR configuration, such verification can take place while the tape is moving in either direction.

The write format of today's data recorders will typically be compatible with more modem metal particle tapes ("MP tapes"). Such newer tape drives can also read older formatted CrO₂ tapes (for example), but may not be able to write the older format.

A disadvantage of such "dual-use" data recorders (for example, those recorders having the capability to read/write MP tapes and read older CrO₂ tapes), is that of CrO₂ tapes in -2-

general: It is known that the older CrO₂ tapes can stick or cling to the head at start-up (i.e., as the reel motor starts to turn and move the tape across the head). (The sticking or clinging has also been referred to as "stiction", a contraction of "static friction," a principle cause.)

When there is such clinging, the tape does not move and the reel motor must pull very hard until the tape comes loose with respect to the head. The clinging degrades the magnetic coating of the tape, and errors in reading and/or writing will eventually result. At times, the tape comes loose with an audible "popping" sound, a particularly damaging circumstance. In the severest cases of clinging, the tape either breaks in two, or the current supplied to the reel motor surpasses its safety level and cannot pull the tape free. In both cases, the tape is rendered useless, with a loss of data or other inconvenience.

Of course, the clinging problem for CrO₂ is aggravated in data recorders having multiple heads, because the tape passes over two heads unnecessarily. (That is, for a dual-use RWR data recorder which only reads a CrO₂ tape, the tape not only passes over the read head that reads the tape, but also passes over a write head and a second read head.) By contrast, the newer MP tapes do not have the magnitude of clinging found in the older CrO₂ tapes. Thus, for "dual use" data recorders it is desirable to minimize the clinging created by reading CrO₂ tapes.

One way clinging was avoided in the past was by directing air pressure to the underside of the tape (between the head and the tape) during start-up and stopping. The air pressure was delivered via conduits with outlets at the surface of the heads. The disadvantage of this system is it is complex and costly. It is thus not well suited for a dual-use system where tapes having clinging problems (such as CrO₂ tapes) are used only part of the time.

Thus, it is an objective of the present invention to provide a dual-use recorder that reduces or eliminates clinging when tapes having clinging problems are used. It is also an objective of the invention to provide such a recorder where the means for eliminating or reducing clinging is simple and cost efficient in view of the limited amount of time such dual- use data recorders will be used with older tapes having clinging problems.

In order to accomplish these objectives, the invention provides a movable lifting mechanism adjacent the multiple heads of a tape drive. The path of the tape and the lifting mechanism is designed such that the lifting mechanism engages the tape in an extended position to alter the tape path such that the tape engages less than all of the heads of the device. In a typical example, for a data recorder having RWR heads being used with the -3-

older CrO₂ tape, the lifting mechanism of the device is configured to engage the tape to alter the tape path such that the tape only engages one of the read heads, and not the write head and the other read head.

The lifting mechanism is also movable into a retracted position which does not alter the path of the tape with respect to the heads. When the lifting mechanism is in the retracted position, the tape engages all heads, such as the RWR heads in the above example. Thus, when a more modern MP tape is used in the exemplary configuration described above, the lifting mechanism is kept in the retracted position.

As will be seen in the detailed description of an exemplary embodiment below, the invention also reduces head wear and tape wear, and generates less tape debris on the heads.

BRIEF DESCRIPTION OF THE DRAWINGS For better understanding of the invention, reference is made to the following drawings which are to be taken in conjunction with the detailed description to follow:

Fig. 1 is a representative drawing of a tape drive having multiple heads of the present invention;

Fig. 2 is a more detailed drawing of the portion of Fig. 1 encircled with dashes, showing a lifting mechanism of the present invention in a retracted position;

Fig. 3 is a more detailed drawing of the portion of Fig. 1 designated by the dashed circle, showing the lifting device of the present invention in an extended position; Fig. 4 is a perspective view of a portion of a tape drive having a number of components illustrated in Figs. 1-3;

Figs. 5 and 6 illustrate an alternative embodiment of a tape drive of the present invention; and

Fig. 7 illustrates another alternative embodiment of a tape drive of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to Fig. 1, a drawing representing a tape drive incorporating the present invention is shown. A tape cartridge 10 interfaces with a first spindle 12 that interfaces with a drive motor (not shown). The tape 14 extends from the cartridge 10, over a number of components (described in more detail below), to a reel 16. The reel 16 interfaces with a second spindle 18, which also interfaces with the drive motor. -4-

Generally, the path of the tape from the cartridge 10 to the reel 16 will be referred to as the "tape path."

Also shown in Fig. 1 are guides 20, 22. Guides 20, 22 have smooth surfaces (which can alternatively be rollers) over which the tape 14 passes. Guides 20, 22 serve to define a portion of the tape path between the cartridge 10 and the reel 16.

Also shown in Fig. 1 is multiple head unit 24. The multiple head unit 24 will be described in further detail below in describing Figs. 2 and 3. As seen in Fig. 1, the relative positioning of the cartridge 10, reel 16, and guides 20, 22 provides the tape path to pass over the magnetic surface 26 of the multiple head unit 24. Fig. 1 also shows a lifting mechanism 28. The lifting mechanism will also be described further below with respect to the description of Figs. 2 and 3. Referring now to Fig. 2, the multiple head unit 24 and lifting mechanism 28 portions of the tape drive of Fig. 1 are shown in more detail. The multiple head unit is shown to have three heads 24a, 24b, 24c, each having a magnetic surface 26a, 26b, 26c. For example, if the multiple head unit 24 is a RWP. configuration, then head 24a would be the forward 23 read head, head 24b would be the write head and head 24c would be the reverse-read head. It follows that magnetic surfaces 26a, 26c of the read heads 24a, 24c would be read-head surfaces and magnetic surface 26b of write head 24b would be a write- head surface. As noted above, such an RWR configuration can read data immediately after being written in order to verify the accuracy of the written data.

Thus, if the tape is moving in the forward direction (shown to be from the cartridge 10 to the reel 16 in Fig. 1), then the forward-read head 24a reads (via the read-head surface 26a) and verifies the accuracy of the data written by write head 24b (via the write-head surface 26b). If the tape is moving in the reverse direction, then the reverse read-head 24c reads and verifies the accuracy of the data written by the write head 24b.

Fig. 2 also shows a moveable lifting mechanism 28 having a engageable roller portion 28a. The lifting mechanism 28 is shown in a retracted position in Fig. 2; that is, the roller portion 28a of the lifting mechanism 28 does not engage the tape 14 and thus does not contribute to definition of the tape path of the tape 14. As also seen in Fig. 2, and as previously noted above, when the lifting mechanism 28 is in the retracted position, the tape path is such that the tape 14 engages each of the magnetic surfaces 26a, 26b, 26c. Thus, if the -5-

heads 24a, 24b, 24c are RJR, as in the example described above, the tape 14 may be written and read for verification in either the forward or reverse direction.

Thus, when the lifting mechanism 28 is in the retracted position as shown in Fig. 2, the tape 14 engages all three magnetic surfaces 26a, 26b, 26c of the heads 24a, 24b, 24c. Accordingly, the surface area engaged by the tape 14 is high; thus, use of a tape 14 having little or no clinging characteristics, such an MP tape, is compatible with this mode of operation (i.e., with the lifting mechanism 28 retracted).

Referring now to Fig. 3, the moveable lifting mechanism 28 is shown in an extended position. In the extended position, the roller portion 28a of the lifting mechanism 28 engages the tape 14 and alters the tape path such that only magnetic surface 26c of head 24c engages the tape. Thus, the surface area contacted by the tape 14 is reduced, because magnetic surfaces 26a, 26b are not contacted.

Thus, when the lifting mechanism 28 is in the extended position as shown in Fig. 3, the device is suitable for a tape that has clinging problems, such as CrO₂ tape, because the surface area of contact of the tape with the heads is reduced.

For the example where the heads 24 are RWR, the head 24c contacted when the lifting mechanism 28 is extended is a reverse-read head. Thus, when a CrO₂ tape is used, the device is suited for reading the tape. (A reverse-read head when used alone in this manner can read in either direction. The "reverse" nomenclature is adopted for the head because, when the head is used together with the write head to verify the data written from the write head (for example, when used with an MP tape as described with respect to Fig. 2 above), the tape 14 would be moving in the reverse direction.)

The use of the tape drive for only reading a CrO₂ tape (when the lifting mechanism 28 is in the extended position) while both writing and reading an MP tape (when the device 28 is in the retracted position as in Fig. 2) does not unnecessarily constrain the use of the device for writing. Since the formats for writing MP tapes is different from the older CrO₂ tapes, the device cannot be used to write both types of tapes. That the tape drive only reads the CrO₂ tapes does not sacrifice versatility of the device.

Fig. 4 is a perspective view of a portion of a tape drive that incorporates many of the features described above with respect to Figs. 1-3. (Thus, analogous features have the same reference numbers in Fig. 4.) The portion shows the two guides 20, 22 on either side of multiple head unit 24. -6-

Fig. 4 also presents a particular construction of lifting mechanism 28 in more detail. Roller portion 28a is seen mounted normally to a shaft 28b via bolt 28c. Shaft 28b projects within guide 28d and moves in an axial direction (thus moving roller 28a in the same direction) . Bolt 28c lies within a recess 28e in guide 28d, which is oblong in the axial direction of the shaft 28b. Movement of shaft 28b (and roller 28a) in the axial direction of the shaft 28b is constrained when the bolt 28c reaches either end of the recess 28e. (A second bolt 28c' at the opposite end of roller 28a is constrained by a second oblong recess 28e' in a second guide 28d'.)

Thus, by comparison to Fig. 3, lifting mechanism 28 in Fig. 4 is shown in the extended position, because bolt 28c is seen to be at the forward end of recess 28e (i.e., that end of the recess that would make the roller 28a engage a tape passing across the guide surfaces 20a, 22a of guides 20, 22). Consequently, as described above with respect to Fig. 3, a tape extended across guide surfaces 20a, 22a would only engage read head 26c.

When the shaft 28b is pulled back, the bolt 28c engages the opposite end of the recess 28e shown in Fig. 4. With the shaft 28b pulled back, the lifting mechanism 28 would be in the retracted position analogous to Fig. 2, and the tape would engage all three magnetic heads 26a, 26b, 26c.

As also shown in Fig. 4, a solenoid unit 28f interfaces with shaft 28b to move the shaft 28b and roller 28a portions of the lifting mechanism 28 between its extended and retracted position. The solenoid unit can be configured to manually or automatically control the position of the mechanism 28. For example, a manual switch could be used to control the solenoid and thus the position of the lifting mechanism 28, depending on the type of tape being used. Alternatively, a switching circuit and/or device could be configured which automatically detects the type of tape that is in use, and positions the lifting mechanism 28 accordingly via the solenoid 28f.

Figs. 5 and 6 are representative drawings of an alternative embodiment of a tape drive such as that shown in Fig. 1. Figs. 5 and 6 show components that are analogous to those shown in Figs. 2 and 3, respectively. Like features in Figs. 5 and 6 are thus designated by adding 100 to the reference numerals in Figs. 2 and 3. In Fig. 5, the lifting mechanism 128 is shown in the retracted position. Thus, all three heads 126a, 126b, 126c are engaged, as in Fig. 2. However, unlike Fig. 2, the lifting mechanism 128 of Fig. 5 engages the tape 114 in the retracted position and thus defines a -7-

portion of the tape path. (Thus, lifting mechanism 128 could replace guide 22 in Fig. 1.) In Fig. 6, the lifting mechanism 128 is in the extended position, and the tape path is altered so that tape 114 only engages head 124c.

Thus, Figs. 5 and 6 illustrate that the tape does not have to be free of the lifting mechanism in the retracted position. The lifting mechanism must only create a change in the tape path such that all heads of the tape drive are engaged when the mechanism is in a first position, and less than all heads of the tape drive are engaged when the mechanism is in a second position. (In fact, the lifting mechanism could actually be a "pushing" mechanism: As shown in the alternative embodiment of Fig. 7, the tape path is such that the tape 214 only engages one head 224c when the mechanism 228 is in a retracted position, shown in solid lines. When the mechanism 228 is in a extended position, shown in dashed lines, the tape path is altered such that the magnetic surfaces of all three heads 224a-c are engaged.)

The above described embodiments are merely illustrations of the present invention. Numerous modifications and adaptations thereof will be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention and the appended claims. For example, while the lifting mechanism of the above embodiments had a roller that engaged the tape to alter the tape path, a smooth surface could be substituted for the roller. Moreover, the particular shape or design of the lifting mechanism, or how it is moved, is not a limitation. Any mechanism which serves to alter the tape path to alter the number of head surfaces engaged by the tape will fall within the scope of the invention. (Thus, the magnetic surfaces of the multiple heads do not necessarily have to be proximate each other or approximately form a contiguous surface, as in the particular embodiments described above.) The lifting mechanism does not even have to be separate from other components of the tape drive. For example, the guide 22 shown in Fig. 1 could also be made moveable and additionally perform the function of the lifting mechanism. (This is also noted in the description of Figs. 5-6 above.) Also, the invention is not limited by the number of heads in the tape drive or their configuration, nor is it limited by the type of tapes used. Thus, the above description should be considered a representative embodiment of the invention and not a limitation on the scope of the invention.

Claims

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WHAT IS CLAIMED IS: 1. A device for handling a magnetic tape, the device comprising: at least two magnetic heads having magnetic surfaces, the surfaces defining at least part of a tape path for a magnetic tape when mounted in the device; and a moveable lifting mechanism having at least first and second positions and altering the tape path when the mechanism is moved between the first position and the second position, the tape path in the first position lying across all the magnetic surfaces of the heads and the tape path in the second position lying across less than all of the magnetic surfaces of the heads.

2. A device as in Claim 1, wherein there are three heads each having a magnetic surface.

3. A device as in Claim 2, wherein the three heads are configured together as a unit, the magnetic surfaces of the three heads approximately forming a contiguous surface.

4. A device as in Claim 3, wherein the three heads are a write head between two read heads.

5. A device as in Claim 1, wherein the first position of the lifting mechanism is a retracted position that does not engage a magnetic tape lying on the tape path, the tape path lying across the magnetic surfaces of all the magnetic heads.

6. A device as claimed in Claim 5, wherein the second position of the lifting mechanism is an extended position that engages a magnetic tape and alters the tape path of the magnetic tape, the altered tape path lying across less than all of the magnetic surfaces of the heads.

7. A device as claimed in Claim 6, wherein there are three heads each having a magnetic surface, the tape path extending across all magnetic surfaces of the three heads when the lifting mechanism is in the first position and extending across one of the magnetic surfaces of the three heads when the lifting mechanism is in the second position.