CA1062807A - Method and apparatus for supporting tape along a path of a rotating head - Google Patents
Method and apparatus for supporting tape along a path of a rotating headInfo
- Publication number
- CA1062807A CA1062807A CA280,665A CA280665A CA1062807A CA 1062807 A CA1062807 A CA 1062807A CA 280665 A CA280665 A CA 280665A CA 1062807 A CA1062807 A CA 1062807A
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- Canada
- Prior art keywords
- rotor
- tape
- head
- air bearing
- mandrel
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
METHOD AND APPARATUS FOR SUPPORTING TAPE
ALONG THE PATH OF A ROTATING HEAD
ABSTRACT
In rotating-head magnetic recording, the rotor carrying the magnetic transducer is enlarged in width so that the width of the rotor is much greater than the track width of the head. The rotor is mounted in the middle of an air bearing mandrel around which magnetic tape is wrapped. The wide rotor also provides an air bearing for the tape. The air bearing for the rotor and mandrel is accomplished by forcing air through their cylindrical surfaces. These cylindrical surfaces may be either a porous material or a nonporous material with holes through which the air may flow.
The wide air bearing rotor provides a very stable platform upon which the magnetic tape may rest while it is scanned by the rotating head.
ALONG THE PATH OF A ROTATING HEAD
ABSTRACT
In rotating-head magnetic recording, the rotor carrying the magnetic transducer is enlarged in width so that the width of the rotor is much greater than the track width of the head. The rotor is mounted in the middle of an air bearing mandrel around which magnetic tape is wrapped. The wide rotor also provides an air bearing for the tape. The air bearing for the rotor and mandrel is accomplished by forcing air through their cylindrical surfaces. These cylindrical surfaces may be either a porous material or a nonporous material with holes through which the air may flow.
The wide air bearing rotor provides a very stable platform upon which the magnetic tape may rest while it is scanned by the rotating head.
Description
18 FIELD OF T~lE I~'~VE2!TION
. .
19 This invention relates to reco~-'ing on magnetic tape with a rotating magnetic transducer.
21 More particularly, the invention relates to providing 22 an air bearing to support the tape in a stable manner 23 along the path of the rotating head. The stability 24 of the air bearing near the path of the rotating head becomes more critical when the rotating head 26 is a flying head rather than a contact head. Any 27 fluttering of the tape due to an unstable air bearing 28 makes it almost impossible to control the flying 1 height or separation between a rotating head and
. .
19 This invention relates to reco~-'ing on magnetic tape with a rotating magnetic transducer.
21 More particularly, the invention relates to providing 22 an air bearing to support the tape in a stable manner 23 along the path of the rotating head. The stability 24 of the air bearing near the path of the rotating head becomes more critical when the rotating head 26 is a flying head rather than a contact head. Any 27 fluttering of the tape due to an unstable air bearing 28 makes it almost impossible to control the flying 1 height or separation between a rotating head and
2 the magnetic tape.
3 HISTORY OF TH~ ART
4 Rotating-head magnetic recording is usually accomplished by wrapping the tape helically about 6 a mandrel split and separated to accommodate a rotating 7 wheel which carries the magnetic head. In other 8 words, the mandrel consists of two separate cylindrical 9 halves which abut a rotating wheel of the same radius as the cylindrical halves, and this rotating wheel 11 carries the magnetic head. In many applications 12 the magnetic tape makes contact with both the mandrel 13 surface and the rotating wheel carrying the magnetic 14 head.
Alternatively, to reduce wear, the mandrel 16 halves have been made air bearing to support the 17 tape as it is wrapped helically about the mandrel.
18 The air bearing support has been achieved hydrostatically 19 and hydrodynamically. With a hydrostatic air bearing the mandrel halves contain holes through which air 21 is forced to provide the air bearing between tape 22 and mandrel. With a hydrodynamic air bearing, the 23 mandrel itself is rotated and the rotating action 24 creates a hydrodynamic air bearing to separate the tape from the mandrel. To date, in both cases, the 26 magnetic head still makes contact with the tape and 27 does not fly relative to the tape.
28 An example of the-hydrostatic air bearing .. , ~ . ' .
_ _ . .. . . . . .
106Z~307 1 mandrel is shown in Shashoua et al, U.S. Patent 3,488,455. In this patent the air bearing is achieved via holes in the mandrel through -~ which air is forced. The rotary wheel or rotor upon which the head is mounted produces its own hydrodynamic air bearing based upon the availability of air from the mandrel and the speed of rotation of the wheel. The head itself contacts the tape as the wheel rotates. Thus, since the head is not flying, the problem of controlling head to tape separation does not exist.
An example of the hydrodynamic air bearing is shown in the J.H.
~ Streets U.S. Patent 3,333,753. In this patent the air bearing is created by rotating one-half of the mandrel and mounting the head on the rotating half of the mandrel. The rotating mandrel half creates an hydrodynamic air bearing for itself and a "squeeze air bearing" for the stationary half of the mandrel as discussed in the patent. The magnetic head in this Streets patent also makes contact with the mag-netic tape. Therefore, the Streets patent does not have the problem of careful control of tape support to assist in controlling head to tape separation while flying a magnetic head relative to the tape.
As can be seen from the above prior art examples, the prior art has taken the approach of keeping the rotating head in contact with the magnetic tape. This technique carries enormous tape wear and head wear problems. These wear problems can be . 106Z~307 1 eliminated by flying the rotating head relative to 2 the tape. One critical problem in flying the rotating 3 head relative to the tape is the necessity of providing 4 stable support for the tape along the path of the rotating head. As is readily apparent, any distur-6 bance which causes a variation in the thickness or 7 depth of an air bearing along the path of the rotating 8 head amplifies the problem of trying to control flying 9 height between the rotating head and the tape. Some sources of perturbations are (1) discontinuity in tape 11 support and (2) lack of concentricity or identical 12 diameter in the two mandrel halves located on each 13 side of the rotor carrying the magnetic head.
14 With regard to concentricity, each air bearing thickness is in the order of 1-3 mils and 16 the flying height relative to the rotating head is 17 in the order of 50 microinches. Accordingly, a 1 18 mil difference in the surface position between mandrel 19 halves, or bet~een the mandrel and the rotor carrying the head has a catastrophic effect on flying height.
21 With regard to discontinuity in tape support, 22 a change from air bearing over the mandrel to no 23 air bearing over the rotor can cause instability 24 in the tape along the path of the rotating head.
This discontinuity may even cause the tape to crash 26 onto the mandrel, the rotor, or the head carried by 27 the rotor. Also a change in type of air bearing 28 from mandrel to rotor can cause instability in the BO972031 ~4~
. .. . ., . . . _ _ .... . . . .. .. ..
1062~07 l tape along the path of the rotating head. Thus, 2 either forcing air out past the rotor in the gap 3 between the rotor and each mandrel half, or relying 4 on a hydrodynamic air bearing for the rotor would still create a discontinuity in the air bearing between 6 mandrel and rotor. The discontinuity causes the 7 tape to wobble or buckle near the path of the rotating 8 head.
9 SUl~MARY OF THE INV~NTION
. In accordance with this invention a stable ll platform for supporting the magnetic tape along the 12 path of the rotating head has been achieved by providing 13 a support for the magnetic tape which is substantially 14 the same as the support provided the tape by the two mandrel halves on each side of the rotor carrying 16 the magnetic head. Preferably, this support is a 17 hydrostatic air bearing for each of the mandrel halves 18 and also for the rotor. Of course, a hydrodynamic 19 effect will also exist with the rotor as the rotor . is in motion. In addition, the width of the rotor 21 . should be substantially greater than the width of 22 the head carried by the rotor, so as to eliminate 23 any perturbation in tape support caused by slight 24 differences in diameter or concentricity between the mandrel halves and the rotor. In other words, the 26 rotor should be designed so that it provides a stable 27 p1atform for the magnetic tape along the path of 28 the rotating head. In this way, the wobble or .
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fluttering of the tape along the path of the rotating 2 head will be eliminated, and flying height between 3 the head and the tape may be more easily controlled.
4 The foregoing and other features and advan-tages of the invention will be apparent from the 6 following more particular descrlption of a preferred 7 embodiment of the invention as illustrated in the 8 accompanying drawings.
FIGURE 1 shows one preferred embodiment 11 of the invention whereln the rotor is much wider 12 than the head, which the rotor carries, and provides 13 an air bearing to the magnetic tape via air forced 14 through holes in the rotor.
FIGURE 2 is a cross-section of the surface 16 of the air bearing rotor bounded by air bearing mandrel 17 halves, and showing the flow of air through the rotor 18 to provide a stable platform for the magnetic tape 19 to ride on along the path of the rotating head.
FIGURE 3 shows a pressurized air-bearing 21 rotor mounted on a shaft with a section cut away 22 to show the construction of the rotor.
24 In FIGURE 1 the pressure rotor 10 is shown mounted between the two mandrel halves 12 and 14.
26 The rotor carries the magnetic head 16 to scan the 27 tape 18. Tape 18 is guided in an arcuate path about 28 the rotary path of the head by being wrapped helically :
. , , . _ ... . . . ..
1 about the mandrel and rotor assembly. Alternatively, 2 the tape might be wrapped. cylindrically about a 3 portion of the mandrel and moved in the direction of 4 the axis of the mandrel.
Rotor 10 has holes in its surface for permit-6 ting air under pressure to flow through the surface 7 of the rotor to provide the air bearing between the 8 rotor and the tape 18. The mandrel halves 12 and 9 14 are also air bearing which is achieved by forcing air through porous material making up the surface 11 of the mandrel. Alternatively, the mandrel halves 12 12 and 14 could have holes in their cylindrical 13 surfaces through which the air could be forced to 14 form the air bearing between the mandrel and the tape 18.
16 FIGURE 1 graphically displays that the 17 rotor 10 is much wider than the head 16 which it 18 carries. This extra width in the rotor, coupled 19 with the fact that the rotor is pressurized to provide an air bearing, provides a stable platform upon which 21 the tape 18 can rest as the rotating head scans across 22 the tape. Stated another way, the preferred stable 23 platform is a continuous uniform air bearing along 24 the path of the rotating head.
Discontinuities in the transition region 26 from mandrel half to rotor no longer affect the flying 27 helght between the rotating head and the tape, because 28 they have been isolated from the path of the rotating BO972031 ~7~
` 1062807 1 head. The isolation is due to the fact that the ajr bearjn~ on the pressurTzed rotor is substantially the same as the air bearing on the mandrel halves 12 and 14, and is also due to the width of the rotor separating the head from the discontinuity in height between rotor and mandrel halYes.
In FIGURE 2 the manner in which the invention provides a stable platform for the tape along the rotary path of the head is clearly shown. The surface of rotor 10 is shown in cross-section between mandrel halves 12 and 14. Head 16 is shown mounted in the rotor 10. The position of the tape 18 is shown as it rides on an air bearing above the pressure rotor 10 and the air bearing mandrel halves 12 and 14. The same elements in FIGURES 1 and 2 have been given the same reference numeral; however, the rotor identified by reference numeral 10 in both figures is slightly different. In FIGURE 1 rotor 10 has a nonporous surface with holes to supply air, while in FIGURE 2 rotor 10 has a porous surface to supply air.
The magnetic head 16 is a flying head which aerodynamically creates a bulge in the tape 18 as the head 16 moves under the tape.
A description of this magnetic head will be found in U.S. Patent No. 3,821,813, issued June 28, 1974 and entitled "Wasp-Waist Head For Flying Flexible Magnetic Storage Medium Over Head".
~06Z807 1 As indicated in FIG~RE 2, the surface of 2 the mandrel halves 12 and 14 and the surface of the 3 rotor 10 are usually at different levels due to 4 dimensional tolerances of components. The difference in level between a rotor and a mandrel half is 6 general,y no more than 1 mil. However, the tape 7 18 is flying in the order of 2-3 mils above the surface 8 of the mandrel or the rotor, and consequently, a 9 level shift of 1 mil in the transition from mandrel to rotor puts a sizable perturbation in the level - ` 11 of the tape 18 above the mandrel or the rotor. This 12 perturbation has been moved laterally away from the 13 rotary path of the head 16 because of the width of 14 the rotor 10. The width of the rotor 10 is not critical, except that it should be sufficient such that pertur-16 bations existing at the discontinuity between mandrel 17 half and rotor will be damped out before they reach 18 the path of the head 16. Stated another way, the 19 rotor 10 has sufficient width so that a stable platform for the tape 18 exists in the immediate area of the 21 head 16.
22 The air bearing in FIGURE 2 is achieved 23 by use of a porous material to form the outer surface 24 of the mandrels 12 and 14 and the rotor 10. Rotor 10 has nonporous sidewalls 20 and 22 which define 26 a plenum chamber 24 which is pressurized~ The porous 27 surface 26 of the rotor then surrounds the head 16 28 and covers the entire outside cylindrical surface ' .
~0972031 - -9-_ . .. . . . .. ...
~062807 1 of the rotor 10. Air under pressure in the plenum 2 chamber 24 is forced into the porous material 26, 3 The air works its way through the porous material 4 and provides a uniform air pressure out the surface of tne porous material adjacent to the tape 18.
6 The flow of air into and out of the porous 7 material is depicted by the arrows in FIGURE 2. Of 8 particular interest is the fact that the corners 9 of the rotor and of the mandrel halves are rounded and made of porous material so that the air passing 11 out of these corners will tend to support the tape 12 in the transition region 28 between a mandrel half 13 and the rotor.
14 The surface of the mandrel halves 12 and 14 is substantially the same as the surface 26 of i 16 the rotor 10. The plenum and sidewalls for the mandrel 17 halves 12 and 14 are not shown in the cut-away of 18 the mandrel halves in FIGURE 2. These do exist and 19 do provide the same type of air bearing out the surface of t~e mandrel halves 12 and 14 just as the air bearing 21 provides out the surface of the rotor 10. The air 22 bearings from both the rotor and mandrel preferably 23 have the same thickness and stiffness.
24 By provi.ding a hydrostatic air bearing in both the mandrel halves and in the rotor, a con-26 tinuity of air bearing or continuity of the support 27 of -~he tape is provided across the mandrel and rotor.
28 This continuity adds substantially to the stability ., .
BO972031 -10~
-... . . ..... ....
f ~ ~( 1 of the tape 18 in the region of the rotary path of 2 head 16. While the manner in which the hydrostatic 3 bearing is achieved is not critical, it is preferable 4 to use the same type of hydrostatic bearing in a rotor as exists in the mandrel halves. The hydrostatic 6 bearing might be achieved by forcing air through 7 a porous material or by forcing air through holes 8 in a nonporous material. The important thing is 9 that the strength of the air bearing should be sub-stantially the same over the rotor as over the mandrel 11 halves, so as to achieve a continuity of air bearing 12 from mandrel half to rotor to other mandrel half.
13 An example of the structure of the pressure 14 rotor is shown in FIGURE 3. The rotor 10 is mounted on a hollow shaft 30. The rotor has a hub 31 which 16 is tied to the shaft via a threaded bolt 32. Inside 17 the rotor is an annular plenum chamber 34 that goes 18 around the entire rotor except in the region 33 where 19 the head is to be mounted. Chamber 36 is provided for mounting a head through the hole 38 in the porous 21 surface 40 of the rotor.
22 The rotor has nonporous walls 42 and 44 23 which support the cylindrical porous surface 40 of 24 the rotor. The nonporous w~lls and hub of the rotor may be constructed of aluminum, for example. Possible 26 choices for the porous surface of the rotor could 27 be sintered bronze or porous ceramics.
-f~
1 Wall 42 is constructed as an integral part 2 of the nonporous hub 31 making up the rotor. Also 3 integrated into this nonporous hub 31 is the chamber 4 36 for mounting the magnetic head.
To provide air to the porous surface 40 6 immediately adjacent the hole 38 for the head, 7 channels 46 and 48 are cut. Channel 46 is cut in 8 the hub 31. Integral with the other wall 44 of the g pressure rotor is the top of the chamber 36. In this top section of the chamber 36, the second channel 11 48 is cut to provide air to the porous surface 40 12 adjaeent the head. Thus the channels 46 and 48 are 13 provided to communicate to the plenum chamber 34 14 sinee the plenum ehamber is not placed in the region 33 of the head mount. Of course, an alternate choice 16 would be to leave the plenum ehamber eompletely annular 17 all around the entire pressure rotor and seal the 18 plenum chamber after the magnetic head has been mounted 19 in the rotor.
Air flow to the plenum chamber 34 is provided 21 through the hollow center 50 of the shaft 30. The 22 shaft eenter 50 eommunieates with an annular ehamber 23 52 in the shaft through a holes 54 (one shown). An 24 annular ehamber 52 communieates to the plenum chamber 34 through holes 56 drilled in the hub 31 at regularly 26 spaced intervals around the hub. Holes 54 in the 27 shart between the shaft center 50 and the annular 28 chamber 52 are also regularly spaced around the shaft.
BO972031 ~12-. .
~0628~7 l Thus air under pressure enters the hollow center 2 50 of the shaft 30, passes throuyh the holes 54 in 3 the shaft, and into the annular chamber 52 of the 4 shaft. From there the air moves into holes 56 (one shown) in the hub 31, and finally to the plenum charrber 6 34 in the pressure rotor.
7 It t~ill be appreciated by one skillea in 8 the art that there are many configurations that the 9 pressure rotor could assume, and that there is nothing critical in the structure of the rotor as shown in 11 FIGURE 3. The significance of the invention is that 12 the rotor is much wider than the magnetic head which 13 it carries. An additional feature is that the rotor 14 provides a bearing for the magnetic tape similar to the bearing provided by the mandrel. As a result, 16 a very stable platform exists to support the magnetic 17 tape all along the entire length of the path of the 18 rotating head.
l9 What is claimed is:
B0372031 - ~13-, _ , , , ,, _ ... . . . .
Alternatively, to reduce wear, the mandrel 16 halves have been made air bearing to support the 17 tape as it is wrapped helically about the mandrel.
18 The air bearing support has been achieved hydrostatically 19 and hydrodynamically. With a hydrostatic air bearing the mandrel halves contain holes through which air 21 is forced to provide the air bearing between tape 22 and mandrel. With a hydrodynamic air bearing, the 23 mandrel itself is rotated and the rotating action 24 creates a hydrodynamic air bearing to separate the tape from the mandrel. To date, in both cases, the 26 magnetic head still makes contact with the tape and 27 does not fly relative to the tape.
28 An example of the-hydrostatic air bearing .. , ~ . ' .
_ _ . .. . . . . .
106Z~307 1 mandrel is shown in Shashoua et al, U.S. Patent 3,488,455. In this patent the air bearing is achieved via holes in the mandrel through -~ which air is forced. The rotary wheel or rotor upon which the head is mounted produces its own hydrodynamic air bearing based upon the availability of air from the mandrel and the speed of rotation of the wheel. The head itself contacts the tape as the wheel rotates. Thus, since the head is not flying, the problem of controlling head to tape separation does not exist.
An example of the hydrodynamic air bearing is shown in the J.H.
~ Streets U.S. Patent 3,333,753. In this patent the air bearing is created by rotating one-half of the mandrel and mounting the head on the rotating half of the mandrel. The rotating mandrel half creates an hydrodynamic air bearing for itself and a "squeeze air bearing" for the stationary half of the mandrel as discussed in the patent. The magnetic head in this Streets patent also makes contact with the mag-netic tape. Therefore, the Streets patent does not have the problem of careful control of tape support to assist in controlling head to tape separation while flying a magnetic head relative to the tape.
As can be seen from the above prior art examples, the prior art has taken the approach of keeping the rotating head in contact with the magnetic tape. This technique carries enormous tape wear and head wear problems. These wear problems can be . 106Z~307 1 eliminated by flying the rotating head relative to 2 the tape. One critical problem in flying the rotating 3 head relative to the tape is the necessity of providing 4 stable support for the tape along the path of the rotating head. As is readily apparent, any distur-6 bance which causes a variation in the thickness or 7 depth of an air bearing along the path of the rotating 8 head amplifies the problem of trying to control flying 9 height between the rotating head and the tape. Some sources of perturbations are (1) discontinuity in tape 11 support and (2) lack of concentricity or identical 12 diameter in the two mandrel halves located on each 13 side of the rotor carrying the magnetic head.
14 With regard to concentricity, each air bearing thickness is in the order of 1-3 mils and 16 the flying height relative to the rotating head is 17 in the order of 50 microinches. Accordingly, a 1 18 mil difference in the surface position between mandrel 19 halves, or bet~een the mandrel and the rotor carrying the head has a catastrophic effect on flying height.
21 With regard to discontinuity in tape support, 22 a change from air bearing over the mandrel to no 23 air bearing over the rotor can cause instability 24 in the tape along the path of the rotating head.
This discontinuity may even cause the tape to crash 26 onto the mandrel, the rotor, or the head carried by 27 the rotor. Also a change in type of air bearing 28 from mandrel to rotor can cause instability in the BO972031 ~4~
. .. . ., . . . _ _ .... . . . .. .. ..
1062~07 l tape along the path of the rotating head. Thus, 2 either forcing air out past the rotor in the gap 3 between the rotor and each mandrel half, or relying 4 on a hydrodynamic air bearing for the rotor would still create a discontinuity in the air bearing between 6 mandrel and rotor. The discontinuity causes the 7 tape to wobble or buckle near the path of the rotating 8 head.
9 SUl~MARY OF THE INV~NTION
. In accordance with this invention a stable ll platform for supporting the magnetic tape along the 12 path of the rotating head has been achieved by providing 13 a support for the magnetic tape which is substantially 14 the same as the support provided the tape by the two mandrel halves on each side of the rotor carrying 16 the magnetic head. Preferably, this support is a 17 hydrostatic air bearing for each of the mandrel halves 18 and also for the rotor. Of course, a hydrodynamic 19 effect will also exist with the rotor as the rotor . is in motion. In addition, the width of the rotor 21 . should be substantially greater than the width of 22 the head carried by the rotor, so as to eliminate 23 any perturbation in tape support caused by slight 24 differences in diameter or concentricity between the mandrel halves and the rotor. In other words, the 26 rotor should be designed so that it provides a stable 27 p1atform for the magnetic tape along the path of 28 the rotating head. In this way, the wobble or .
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fluttering of the tape along the path of the rotating 2 head will be eliminated, and flying height between 3 the head and the tape may be more easily controlled.
4 The foregoing and other features and advan-tages of the invention will be apparent from the 6 following more particular descrlption of a preferred 7 embodiment of the invention as illustrated in the 8 accompanying drawings.
FIGURE 1 shows one preferred embodiment 11 of the invention whereln the rotor is much wider 12 than the head, which the rotor carries, and provides 13 an air bearing to the magnetic tape via air forced 14 through holes in the rotor.
FIGURE 2 is a cross-section of the surface 16 of the air bearing rotor bounded by air bearing mandrel 17 halves, and showing the flow of air through the rotor 18 to provide a stable platform for the magnetic tape 19 to ride on along the path of the rotating head.
FIGURE 3 shows a pressurized air-bearing 21 rotor mounted on a shaft with a section cut away 22 to show the construction of the rotor.
24 In FIGURE 1 the pressure rotor 10 is shown mounted between the two mandrel halves 12 and 14.
26 The rotor carries the magnetic head 16 to scan the 27 tape 18. Tape 18 is guided in an arcuate path about 28 the rotary path of the head by being wrapped helically :
. , , . _ ... . . . ..
1 about the mandrel and rotor assembly. Alternatively, 2 the tape might be wrapped. cylindrically about a 3 portion of the mandrel and moved in the direction of 4 the axis of the mandrel.
Rotor 10 has holes in its surface for permit-6 ting air under pressure to flow through the surface 7 of the rotor to provide the air bearing between the 8 rotor and the tape 18. The mandrel halves 12 and 9 14 are also air bearing which is achieved by forcing air through porous material making up the surface 11 of the mandrel. Alternatively, the mandrel halves 12 12 and 14 could have holes in their cylindrical 13 surfaces through which the air could be forced to 14 form the air bearing between the mandrel and the tape 18.
16 FIGURE 1 graphically displays that the 17 rotor 10 is much wider than the head 16 which it 18 carries. This extra width in the rotor, coupled 19 with the fact that the rotor is pressurized to provide an air bearing, provides a stable platform upon which 21 the tape 18 can rest as the rotating head scans across 22 the tape. Stated another way, the preferred stable 23 platform is a continuous uniform air bearing along 24 the path of the rotating head.
Discontinuities in the transition region 26 from mandrel half to rotor no longer affect the flying 27 helght between the rotating head and the tape, because 28 they have been isolated from the path of the rotating BO972031 ~7~
` 1062807 1 head. The isolation is due to the fact that the ajr bearjn~ on the pressurTzed rotor is substantially the same as the air bearing on the mandrel halves 12 and 14, and is also due to the width of the rotor separating the head from the discontinuity in height between rotor and mandrel halYes.
In FIGURE 2 the manner in which the invention provides a stable platform for the tape along the rotary path of the head is clearly shown. The surface of rotor 10 is shown in cross-section between mandrel halves 12 and 14. Head 16 is shown mounted in the rotor 10. The position of the tape 18 is shown as it rides on an air bearing above the pressure rotor 10 and the air bearing mandrel halves 12 and 14. The same elements in FIGURES 1 and 2 have been given the same reference numeral; however, the rotor identified by reference numeral 10 in both figures is slightly different. In FIGURE 1 rotor 10 has a nonporous surface with holes to supply air, while in FIGURE 2 rotor 10 has a porous surface to supply air.
The magnetic head 16 is a flying head which aerodynamically creates a bulge in the tape 18 as the head 16 moves under the tape.
A description of this magnetic head will be found in U.S. Patent No. 3,821,813, issued June 28, 1974 and entitled "Wasp-Waist Head For Flying Flexible Magnetic Storage Medium Over Head".
~06Z807 1 As indicated in FIG~RE 2, the surface of 2 the mandrel halves 12 and 14 and the surface of the 3 rotor 10 are usually at different levels due to 4 dimensional tolerances of components. The difference in level between a rotor and a mandrel half is 6 general,y no more than 1 mil. However, the tape 7 18 is flying in the order of 2-3 mils above the surface 8 of the mandrel or the rotor, and consequently, a 9 level shift of 1 mil in the transition from mandrel to rotor puts a sizable perturbation in the level - ` 11 of the tape 18 above the mandrel or the rotor. This 12 perturbation has been moved laterally away from the 13 rotary path of the head 16 because of the width of 14 the rotor 10. The width of the rotor 10 is not critical, except that it should be sufficient such that pertur-16 bations existing at the discontinuity between mandrel 17 half and rotor will be damped out before they reach 18 the path of the head 16. Stated another way, the 19 rotor 10 has sufficient width so that a stable platform for the tape 18 exists in the immediate area of the 21 head 16.
22 The air bearing in FIGURE 2 is achieved 23 by use of a porous material to form the outer surface 24 of the mandrels 12 and 14 and the rotor 10. Rotor 10 has nonporous sidewalls 20 and 22 which define 26 a plenum chamber 24 which is pressurized~ The porous 27 surface 26 of the rotor then surrounds the head 16 28 and covers the entire outside cylindrical surface ' .
~0972031 - -9-_ . .. . . . .. ...
~062807 1 of the rotor 10. Air under pressure in the plenum 2 chamber 24 is forced into the porous material 26, 3 The air works its way through the porous material 4 and provides a uniform air pressure out the surface of tne porous material adjacent to the tape 18.
6 The flow of air into and out of the porous 7 material is depicted by the arrows in FIGURE 2. Of 8 particular interest is the fact that the corners 9 of the rotor and of the mandrel halves are rounded and made of porous material so that the air passing 11 out of these corners will tend to support the tape 12 in the transition region 28 between a mandrel half 13 and the rotor.
14 The surface of the mandrel halves 12 and 14 is substantially the same as the surface 26 of i 16 the rotor 10. The plenum and sidewalls for the mandrel 17 halves 12 and 14 are not shown in the cut-away of 18 the mandrel halves in FIGURE 2. These do exist and 19 do provide the same type of air bearing out the surface of t~e mandrel halves 12 and 14 just as the air bearing 21 provides out the surface of the rotor 10. The air 22 bearings from both the rotor and mandrel preferably 23 have the same thickness and stiffness.
24 By provi.ding a hydrostatic air bearing in both the mandrel halves and in the rotor, a con-26 tinuity of air bearing or continuity of the support 27 of -~he tape is provided across the mandrel and rotor.
28 This continuity adds substantially to the stability ., .
BO972031 -10~
-... . . ..... ....
f ~ ~( 1 of the tape 18 in the region of the rotary path of 2 head 16. While the manner in which the hydrostatic 3 bearing is achieved is not critical, it is preferable 4 to use the same type of hydrostatic bearing in a rotor as exists in the mandrel halves. The hydrostatic 6 bearing might be achieved by forcing air through 7 a porous material or by forcing air through holes 8 in a nonporous material. The important thing is 9 that the strength of the air bearing should be sub-stantially the same over the rotor as over the mandrel 11 halves, so as to achieve a continuity of air bearing 12 from mandrel half to rotor to other mandrel half.
13 An example of the structure of the pressure 14 rotor is shown in FIGURE 3. The rotor 10 is mounted on a hollow shaft 30. The rotor has a hub 31 which 16 is tied to the shaft via a threaded bolt 32. Inside 17 the rotor is an annular plenum chamber 34 that goes 18 around the entire rotor except in the region 33 where 19 the head is to be mounted. Chamber 36 is provided for mounting a head through the hole 38 in the porous 21 surface 40 of the rotor.
22 The rotor has nonporous walls 42 and 44 23 which support the cylindrical porous surface 40 of 24 the rotor. The nonporous w~lls and hub of the rotor may be constructed of aluminum, for example. Possible 26 choices for the porous surface of the rotor could 27 be sintered bronze or porous ceramics.
-f~
1 Wall 42 is constructed as an integral part 2 of the nonporous hub 31 making up the rotor. Also 3 integrated into this nonporous hub 31 is the chamber 4 36 for mounting the magnetic head.
To provide air to the porous surface 40 6 immediately adjacent the hole 38 for the head, 7 channels 46 and 48 are cut. Channel 46 is cut in 8 the hub 31. Integral with the other wall 44 of the g pressure rotor is the top of the chamber 36. In this top section of the chamber 36, the second channel 11 48 is cut to provide air to the porous surface 40 12 adjaeent the head. Thus the channels 46 and 48 are 13 provided to communicate to the plenum chamber 34 14 sinee the plenum ehamber is not placed in the region 33 of the head mount. Of course, an alternate choice 16 would be to leave the plenum ehamber eompletely annular 17 all around the entire pressure rotor and seal the 18 plenum chamber after the magnetic head has been mounted 19 in the rotor.
Air flow to the plenum chamber 34 is provided 21 through the hollow center 50 of the shaft 30. The 22 shaft eenter 50 eommunieates with an annular ehamber 23 52 in the shaft through a holes 54 (one shown). An 24 annular ehamber 52 communieates to the plenum chamber 34 through holes 56 drilled in the hub 31 at regularly 26 spaced intervals around the hub. Holes 54 in the 27 shart between the shaft center 50 and the annular 28 chamber 52 are also regularly spaced around the shaft.
BO972031 ~12-. .
~0628~7 l Thus air under pressure enters the hollow center 2 50 of the shaft 30, passes throuyh the holes 54 in 3 the shaft, and into the annular chamber 52 of the 4 shaft. From there the air moves into holes 56 (one shown) in the hub 31, and finally to the plenum charrber 6 34 in the pressure rotor.
7 It t~ill be appreciated by one skillea in 8 the art that there are many configurations that the 9 pressure rotor could assume, and that there is nothing critical in the structure of the rotor as shown in 11 FIGURE 3. The significance of the invention is that 12 the rotor is much wider than the magnetic head which 13 it carries. An additional feature is that the rotor 14 provides a bearing for the magnetic tape similar to the bearing provided by the mandrel. As a result, 16 a very stable platform exists to support the magnetic 17 tape all along the entire length of the path of the 18 rotating head.
l9 What is claimed is:
B0372031 - ~13-, _ , , , ,, _ ... . . . .
Claims (3)
1. Apparatus for supporting magnetic tape uniformly along the path of a rotating non-contact head for reading and writing information in tracks oriented at an acute angle relative to the direction of motion of the tape, said apparatus comprising:
wide rotor means for carrying the magnetic head in a rotary path;
means for supporting the tape with an air bearing in an arcuate path, said support means flanking both sides of said rotor means;
said rotor means having means for supporting the tape along said rotary path with an air bearing and having a width substantially greater than the track width of the head whereby perturbations in tape support are damped out as the tape moves from said support means to said rotor means before the tape reaches the rotary path of the head.
wide rotor means for carrying the magnetic head in a rotary path;
means for supporting the tape with an air bearing in an arcuate path, said support means flanking both sides of said rotor means;
said rotor means having means for supporting the tape along said rotary path with an air bearing and having a width substantially greater than the track width of the head whereby perturbations in tape support are damped out as the tape moves from said support means to said rotor means before the tape reaches the rotary path of the head.
2. The apparatus of claim 1 wherein said rotor means provides the same type of air bearing support to the tape as said support means so that there is continuity of support as said tape moves across said sup-port means and said rotor means whereby perturbations in the tape support at transition regions between said support means and said rotor means are reduced.
3. The apparatus of claim 2 wherein the air bearing provided by both said guide means and said rotor means is substantially a hydrostatic air bearing of the same stiffness for both said support means and said rotor means.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA280,665A CA1062807A (en) | 1973-04-02 | 1977-06-16 | Method and apparatus for supporting tape along a path of a rotating head |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US00347089A US3840894A (en) | 1973-04-02 | 1973-04-02 | Wide rotor for stable support of tape along path of transducer carried by rotor |
| CA195,654A CA1056053A (en) | 1973-04-02 | 1974-03-21 | Method and apparatus for supporting tape along a path of a rotating head |
| CA280,665A CA1062807A (en) | 1973-04-02 | 1977-06-16 | Method and apparatus for supporting tape along a path of a rotating head |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1062807A true CA1062807A (en) | 1979-09-18 |
Family
ID=27163383
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA280,665A Expired CA1062807A (en) | 1973-04-02 | 1977-06-16 | Method and apparatus for supporting tape along a path of a rotating head |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1062807A (en) |
-
1977
- 1977-06-16 CA CA280,665A patent/CA1062807A/en not_active Expired
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