Burnishing tape handling apparatus and method

A burnishing tape apparatus includes pads that press the burnishing tape against the surfaces of the disk to be burnished. The pads are mounted on pad holders that are biased to press the pads against both sides of the disk. Tape guides are used to apply tension to the burnishing pad when the pads are moved away from the disk. When the pads are away from the disk tape guides hold the burnishing tape away from the pads so that the burnishing tape may be indexed without damaging or dislodging the pads. As the pads are moved into contact with the disk, the tape guides release the tension on the burnishing tape while the centering guides ensure that the burnishing tape is centered on the pads. By releasing tension on the burnishing tape, the pads are permitted to press the approximate center of the burnishing tape against the surfaces of the disk without deforming in an uncontrolled manner.

FIELD OF THE INVENTION
 The present invention relates to an apparatus and method for burnishing the
 surfaces of a disk, and more specifically burnishing the surfaces of a
 disk with burnishing tape and pads.
 BACKGROUND
 Magnetic memory disks, such as the type typically used in a computer hard
 drive, have a smooth surface over which the read/write head flies during
 operation. The trend has been to reduce the fly height of the read/write
 head over the surface of the disk to increase the data recording density
 on the disk. While it is desirable for a read/write head to fly as close
 as possible to the surface of the disk, it is important that the
 read/write head does not contact the disk or defects on the surface of the
 disk. A defect on the surface of the disk that physically contacts the
 read/write head may damage the read/write head, the disk, or both.
 Consequently, care must be taken during the disk processing and testing to
 assure that there are no defects on the surface of the disk that are
 greater than the fly height of the read/write head, which today is
 approximately 1 .mu." (microinch) or less.
 Typical magnetic disks include an aluminum, glass, or silicon substrate
 that is plated with a NiP (nickel phosphate) layer and then textured,
 e.g., for the contact start stop zone. An underlayer of Cr (chromium) or
 NiP is sputtered on the plated NiP layer, a thin film of magnetic
 recording material, typically a Co (cobalt) alloy, is sputtered on the
 underlayer, followed by the deposition of a protective coating and a
 lubrication layer. The disk is then burnished to remove any asperities
 prior to testing the disk to assure the disk meets the required surface
 specifications. Presently, some magnetic disks are specified to have a
 roughness less than or equal to about 30 angstroms (3 nanometers).
 In conventional methods of burnishing the surfaces of a disk, an abrasive
 burnishing tape is used. Prior art devices for burnishing a disk with an
 abrasive tape include the use of air knives and rollers and in some
 instances the combination of the two. A disadvantage with the use of air
 knives and rollers is that it is difficult to control the force used to
 press the burnishing tape against the disk and to ensure that an equal
 amount of force is applied to both sides of the disk. Without precise
 control of the force applied to both sides of the disk, one side of the
 disk may be burnished more than the other. Further, if one side of the
 disk has a much greater force applied to it than the other, the disk may
 be damaged. In addition, with air knives it is difficult to control the
 precise area of the burnishing tape that is pressed against the disk. It
 is also difficult to burnish with an adequate amount of force without
 scratching the surface of the disk. Further, rollers are difficult to keep
 flat against the surface of the disk.
 SUMMARY
 A burnishing head in accordance with an embodiment of the present invention
 includes burnishing pads that press a burnishing tape against the surfaces
 of a disk. The pads are mounted on pad holders that move to press the
 burnishing tape against the surfaces of the disk with the pads. The
 burnishing apparatus also includes tape guides that hold the burnishing
 tape away from the pads when the pads are not pressed against the surfaces
 of the disk. With the burnishing tape separated from the pads, the
 burnishing tape may be indexed without damaging or dislodging the pads
 from the pad holders. As the pad holders move the pads away from the disk,
 the tape guides apply tension to the burnishing tape used to keep the
 burnishing tape from contacting the pads. As the pad holders move the pads
 into contact with the disk, the tape guides release tension on the
 burnishing tape to prevent uncontrolled deformation of the pads.
 Consequently, the entire footprint of each pad is used to press the
 burnishing tape into contact with the surfaces of the disk.
 The burnishing apparatus operates by mounting a disk on a disk handling
 apparatus, such as a motor driven spindle. The disk is then moved between
 the pads of the burnishing apparatus. As the pads are moved to press the
 burnishing tape against the surfaces of the disk, the tape guides release
 tension on the burnishing tape. Because there is little or no tension on
 the burnishing tape during the burnishing process, the entire footprint of
 the pads press the burnishing tape against the surfaces of the disk.
 Once the disk is burnished, the pad holders are separated, e.g., by way of
 a pneumatic actuator or a stepper motor. As the pads are moved away from
 the surface of the disk, tension is applied to the burnishing tape. The
 burnishing tape is held away from the pads as the burnishing tape is
 indexed. Additionally, the disk is removed from between the burnishing
 pads, and the disk is replaced with the next disk to be burnished. The
 next disk is then moved between the pads, which then are moved to press an
 unused portion of the burnishing tape into contact with the surfaces of
 the next dish.
 In accordance with another embodiment of the present invention, the pads
 are mounted on pad holders that are coupled together with a tension
 spring. The tension spring biases the pad holders together such that the
 pads automatically press against the surfaces of the disk with an equal
 amount of force. The pad holders are slidably mounted on a rail which
 permits the pad holders to slide away from and toward each other. The pad
 holders have the freedom to slide in unison so that when the pads are
 pressed against the surfaces of the disk, the pads automatically align
 with the center of the disk. A separating mechanism, such as a pneumatic
 actuator, is used to overcome the bias of the spring and to move the pads
 away from the disk, for example, when the disk is being replaced and the
 burnishing tape is indexed.

DETAILED DESCRIPTION
 FIG. 1 is a top view of a magnetic disk 101 being burnished by a burnishing
 apparatus 100 in accordance with an embodiment of the present invention.
 The burnishing apparatus 100 uses burnishing pads 106 and 108 to press a
 burnishing tape (not shown in FIG. 1) against the surfaces of a magnetic
 disk 101 while magnetic disk 101 rotates about a spindle 102 as indicated
 by arrow 102a. As can be seen, burnishing pads 106 and 108 are static,
 non-rolling pads. Disk 101 is shown in a side view in FIG. 1. Burnishing
 apparatus 100 may be used to burnish not only magnetic disks, but any
 other disk, including, e.g., optical or magneto-optical disks.
 Disk 101 is shown mounted on disk handling hardware including a spindle 102
 that is driven by a motor 103 to rotate disk 101 at high speed, e.g., 500
 inches per second (ips). The angular velocity, however, may range from 300
 ips to 1000 ips, depending on the amount of burnishing desired and the
 length of processing time, i.e., the higher the angular velocity of disk
 101, the shorter the processing time, but less burnishing will occur. In
 some embodiments, a constant linear velocity (CLV) may be used that vary
 from, e.g., 30 meters/minute to 300 meters/minute.
 As disk 101 rotates, a burnishing surface of an abrasive burnishing tape is
 brought into contact with disk 101. Burnishing tape is pressed against
 both surfaces 104, 105 of disk 101 by pads 106 and 108, respectively, to
 burnish surfaces 104, 105. While disk 101 rotates about spindle 102, disk
 101, spindle 102 and motor 103 are moved in a lateral direction, as
 illustrated by arrow 107, such that approximately the entire area of
 surfaces 104, 105 of disk 101, from the inside diameter to the outside
 diameter or vice versa, may be brought into contact with the burnishing
 tape and thereby burnished.
 Once the burnishing of disk 101 is complete, disk 101, spindle 102 and
 motor 103 are moved away from burnishing apparatus 100, the rotation of
 disk 101 is stopped and disk 101 is removed from spindle 102. By moving
 disk 101 away from burnishing apparatus 100, disk 101 may be easily
 removed from spindle 102. A new disk to be burnished is then mounted on
 spindle 102. The rotation of the new disk is initiated and the new disk
 and spindle 102 are moved laterally between burnishing pads 106 and 108 to
 be burnished. It should be understood the lateral movement between disk
 101 and burnishing apparatus 100 is relative. Thus, if desired, burnishing
 apparatus 100 may be moved laterally while disk 101, spindle 102 and motor
 103 are held stationary as disk 101 rotates about spindle 102.
 Pads 106, 108 are mounted on pad holders 110, 112, respectively, which are
 mounted on respective carriages 114, 116. Carriages 114, 116 are mounted
 on a rail 118. It should be understood that if desired pad holders 110,
 112 may be mounted on rail 118 without intervening carriages 114, 116.
 Thus, carriages 114, 116 actually function as an extension of pad holders
 110, 112 that is mounted on rail 118 and therefore may be considered part
 of pad holders 110, 112. Rail 118 is, e.g., a ball bearing linear slide
 rail or any other type of device that will permit carriages 114, 116 to
 move linearly back and forth perpendicular to the plane of disk 101 with
 little friction. A tension spring 122 connected between carriage 114 and
 carriage 116 is used to bias pads 106 and 108 together. Thus, as
 illustrated by arrows 115 and 117, respectively, carriages 114, 116 along
 with pad holders 110, 112 and pads 106, 108 move towards disk 101 to press
 pads 106, 108 against disk 101, i.e., in a "closed position," as shown in
 FIG. 1. Of course, during burnishing operations a burnishing tape is
 placed between burnishing pads 106 and 108 and sides 104 and 105,
 respectively. Rail 118 includes an inlet connector 120 for an air supply
 that is used to pneumatically separate carriages 114, 116. Thus, as
 illustrated by arrows 115 and 117, respectively, carriages 114, 116 along
 with pad holders 110, 112 and pads 106, 108 may be moved away from disk
 into an "open position." Of course, carriages 114, 116 need not be
 separated pneumatically, but may be separated by any desired manner to
 place pads 106, 108 into an open position.
 With the use of tension spring 122 coupled to carriages 114, 116, pads 106
 and 108 are biased together. Consequently, an equal amount of pressure is
 applied to surfaces 104, 105 of disk 101. By applying the same amount of
 pressure on surfaces 104 and 105 with pads 106 and 108, respectively,
 surfaces 104 and 105 will receive the same amount of burnishing. In
 addition, the equal application of pressure by pads 106, 108 results in no
 net force being applied to disk 101 thereby avoiding damage to disk 101.
 Moreover, carriages 114, 116 are mounted on rail 118 such that carriages
 114, 116 float, i.e., carriages 114, 116 move together in unison as
 illustrated by arrow 119. Because carriages 114, 116 move together in
 unison, pads 106, 108 will be centered on disk 101. Thus, carriages 114
 and 116 are automatically aligned with disk 101, thereby avoiding damage
 to disk 101 when pads 106, 108 are placed in contact with disk 101.
 Carriages 114 and 116 have approximately 0.250" of float or movement that
 accommodates any non-centered condition of disk 101 and will thereby
 maintain equal pressure on surfaces 104 and 105. Thus, if disk 101 is not
 centered, carriages 114 and 116 will move together to place disk 101 in
 the center of pads 106 and 108.
 FIG. 2 shows a top plan view of disk 101 mounted on spindle 102 with pad
 106 pressing a portion of burnishing tape 126 against surface 104. In
 accordance with one embodiment of the present invention, burnishing tape
 126 extends tangentially over disk 101, as shown in FIG. 2. Thus, as pad
 106 presses burnishing tape 126 against surface 104, the edges of
 burnishing tape 126 will not contact disk 101. Consequently, the edges of
 burnishing tape 126 will not scratch or otherwise damage disk 101. In
 addition, burnishing tape 126 has enough surface tension that when pad 106
 presses tape 126 against surface 104, the only portion of tape 126 that
 contacts surface 104 is below the footprint of pad 106. By ensuring that
 only the portion of burnishing tape 126 that is below the footprint of pad
 106 is in contact with surface 104, the amount of burnishing by tape 126
 may be precisely controlled, e.g., by changing the pad size. It should be
 understood that another burnishing tape is similarly pressed into contact
 with surface 105 by pad 108, but is hidden from view in FIG. 2.
 Burnishing tape 126 may be any tape with an appropriate roughness to
 burnish disk 101. One example of burnishing tape 126 is 1 micron Alumina
 manufactured by Mypox of Japan.
 Pads 106, 108 may be any soft material, such as neoprene rubber, that is
 deformable during use and preferably has anti-static properties. Pads 106,
 108 are approximately 5 mm.times.12 mm or 5 mm.times.10 mm, with a
 thickness of 2.5 mm. An example of a material that may be used as pads
 106, 108 is the neoprene rubber material model number 4701-40, formerly
 manufactured by Rubitex of Texas.
 FIGS. 3 and 4 show front views of burnishing apparatus 100 with pads 106,
 108 in the "open position" (i.e., not in contact with disk 101) and in the
 "closed position" (i.e., pressing against disk 101), respectively. As
 shown in FIGS. 3 and 4, burnishing apparatus 100 also includes tape
 handling hardware, which generates the desired tension in the burnishing
 tape while pads 106, 108 are in the open and closed positions. FIGS. 3 and
 4 do not show carriages 114, 116, tension spring 122, or rail 118 for the
 sake of clarity.
 FIG. 3 shows pads 106 and 108, mounted on respective pad holders 110 and
 112, in the open position. Burnishing tapes 126 and 128 extend from
 respective supply reels 130, 132 to respective take-up reels 134, 136. For
 the sake of clarity and simplicity, the path of burnishing tape 126 will
 be described with the understanding that the path of burnishing tape 128
 is the same but in mirror image.
 Burnishing tape 126 extends over rollers 138, 140, and 142, which are
 mounted on an upper tape tracking assembly 144. Burnishing tape 126
 extends around a first tape guide roller 146, over two centering guides
 148 and 150 and around a second tape guide roller 152. Tape guide rollers
 146, 152 are mounted on pad holder 110, while centering guides 148, 150
 are mounted on arms 154, 156, respectively, which are connected to upper
 tape tracking assembly 144 via an intermediate arm 158. Burnishing tape
 126 then continues through a tape guide 160, around a capstan assembly
 with rollers 162 and 164 and is received by take-up reel 134.
 The upper tape tracking assembly 144 and centering guides 148, 150, along
 with the various associated arms, are held in a fixed position. Pad holder
 110 with pad 106, however, is not fixed, and may move laterally as
 illustrated by arrow 166 so that pad 106 may be placed into a closed
 position, as shown in FIG. 4, or an open position as shown in FIG. 3.
 FIG. 4 shows burnishing apparatus with pads 106 and 108 in a closed
 position pressing against disk 101. As can be seen in FIG. 4, pad holder
 110 has moved toward disk 101 relative to centering guides 148, 150.
 FIG. 5 is a simplified top view of burnishing apparatus 100 in an open
 position shown along dimensions A--A as illustrated in FIG. 3. FIG. 6 is a
 simplified top view of burnishing apparatus 100 in a closed position shown
 along dimensions B--B as illustrated in FIG. 4. FIGS. 5 and 6 show pad
 holder 110, 112 mounted on carriages 114, 116, which are mounted on rail
 118. Also shown in FIGS. 5 and 6 is the spring 122 biasing pad holders 110
 and 112 together. Burnishing tapes 126 and 128 and part of the tape
 handling hardware, i.e., supply reel 130, upper tape tracking assembly
 144, tape guide 160, rollers 162, 164 and take-up reel 134, are not shown
 in FIGS. 5 and 6 for the sake of clarity.
 As illustrated in FIGS. 3 and 5, when pad holder 110 is in an open
 position, pad 106 does not contact burnishing tape 126. As discussed
 above, pad holder 110 is pneumatically forced into an open position. When
 placed in an open position, pad holder 110 is moved away from disk 101 by
 an amount sufficient to ensure that pad 106 does not contact burnishing
 tape 126 and to cause tape guide rollers 146, 152 to press against tape
 126 applying tension to tape 126. Pad holder 110 may move approximately
 0.250" to 0.375" when transitioning from a closed position (with pads 106
 and 108 in contact with disk 101) to an open position. When in an open
 position, pad 106 is approximately 1 mm away from burnishing tape 126.
 Centering guides 148, 150, which are held stationary relative to pad
 holder 110, hold burnishing tape 126 away from pad 106. With pad holder
 110 in the open position, disk 101 is moved from between pads 106 and 108.
 Disk 101 may then be removed and replaced with another disk to be
 burnished. Meanwhile, tape 126 is indexed so that an unused portion of
 burnishing tape 126 is placed in front of pad 106. Because centering
 guides 148, 150 hold burnishing tape 126 away from pad 106 while tape 126
 is indexed, burnishing tape 126 may be advanced without damaging or
 dislodging pad 106. Consequently, the life of pad 106 is increased. When
 pad holder 110 is placed in a closed position (as shown in FIGS. 4 and 6)
 an unused portion of burnishing tape 126 will be between pad 106 and disk
 101.
 A motor (not shown) connected to take-up reel 134 rotates take-up reel 134
 by the appropriate amount to index the burnishing tape 126. In addition,
 the capstan assembly, shown as rollers 162 and 164 in FIG. 3, may be
 driven by a motor to index the burnishing tape. A spring on the supply
 reel 130 provides the appropriate amount of resistance in the rotation of
 supply reel 130 to maintain tension on tape 126 as the motor driven
 take-up reel 134 indexes tape 126. Supply reel 130 is discussed in more
 detail in reference to FIG. 10.
 Pad holder 110 is placed in a closed position by decreasing the pneumatic
 force below the bias force of tension spring 122 (shown in FIGS. 5 and 6).
 Thus, pad holder 110 along with tape guide rollers 146, 152 moves toward
 disk 101 into the closed position (shown in FIG. 4 and 6). Because tape
 guide rollers 146, 152 move toward disk 101 when in the closed position,
 tension that was applied by tape guide rollers 146, 152 when in the open
 position is relieved. There is little or no tension applied to burnishing
 tape 126 when the burnishing pads are pressed against the disk, as
 illustrated in FIG. 4. Consequently, when pad 106 presses burnishing tape
 126 against surface 104 of disk 101, pad 106 will not be deformed from
 tension on burnishing tape 126. Thus, burnishing tape 126 is pressed
 against disk 101 by the entire surface area of pad 106. If there is
 tension on burnishing tape 126 as pad 106 presses against disk 101, the
 corners and sides of pad 106 would be deformed by tape 126 causing only a
 central portion of the surface area of pad 106 to press tape 126 against
 disk 101. This would cause a loss of efficiency in the burnishing of disk
 101, as well as less control over the equalization of burnishing on both
 sides of disk 101.
 In addition, as pad holder 110 moves forward toward disk 101, centering
 guides 148, 150 center burnishing tape 126 with respect to pad 106. The
 flanges on centering guides 148, 150 and the flanges on tape guide rollers
 146, 152 hold tape 126 such that it is centered on pad 106 as pad holder
 110 moves into the closed position. Thus, when pad 106 makes contact with
 burnishing tape 126, pad 106 is centered on the tape 126.
 FIGS. 7A, 7B, 7C are detailed top, side and front views, respectively of
 burnishing apparatus 100 without burnishing tape 126, 128, arms 154, 156
 or centering guides 148, 150. As shown in FIGS. 7A, 7B, and 7C, rail 118
 is connected to a pneumatic apparatus 169 for opening pad holders 110,
 112. of course any other means for opening pad holders 110, 112 may be
 used. Pneumatic apparatus 169 is a conventional pneumatic rotary cylinder,
 such as Model P/N manufactured by Shunck Corporation.
 FIG. 8 shows an exploded perspective view of burnishing apparatus 100 where
 only one side of burnishing apparatus 100 is illustrated for the sake of
 clarity. FIG. 8 also shows the tape handling mechanism.
 As shown in FIG. 8, burnishing apparatus 100 includes pad holder 110 upon
 which are mounted tape guide rollers 146 and 152. Pad holder 110 includes
 a depression 113 in which pad 106 is mounted. Pad 106 may be mounted using
 a rubber based glue such as BHE Adhesive or High Strength 90 Adhesive
 manufactured by 3M. Of course, pad 110 may use any mounting surface and
 does not necessarily require a depression. Pad 106 is not shown mounted on
 pad holder 110 in FIG. 7 for the sake of clarity. Pad holder 110 is
 mounted on carriage 114 with pin 115 passing through a central orifice 111
 in pad holder 110. It should be understood that if desired, carriage 114
 and pad holder 110 may be one unit. Thus, one unit may serve as both pad
 holder 110 and carriage 114. A bolt (not shown) may be used to tighten pad
 holder 110 on pin 115. Also mounted on carriage 114 is a spring tension
 arm 170 upon which is mounted tension spring 122 via bolt 123. Tension
 spring 122 is also mounted on the complementary spring tension arm on the
 other pad holder 110. Tension spring 122 is, e.g., part number 185-A
 spring manufactured by Century of Los Angeles, Calif. When in the closed
 position, spring 122 provides a force of approximately 100 grams.
 Centering guides 148, 150 are mounted onto arms 154, 156 via pins 149, 151,
 respectively. Pins 149, 151 may serve as axes about which centering guides
 148, 150 rotate or, alternatively, may simply hold centering guides 148,
 150 which do not rotate. Centering guides 148, 150 may be manufactured
 from Teflon or other similar material. Arms 154, 156 are mounted on an
 intermediate arm 158. Arms 154, 156 may of course be mounted on any
 element that is stationary relative to the movement of pad holder 110,
 such as a wall.
 Intermediate arm 158 is mounted to upper tape tracking assembly 144, which
 is mounted on back plate 143 with guide pin 145. FIGS. 9A and 9B show
 respective side and top views of upper tape tracking assembly along with
 intermediate arm 158 and centering guides 148, 150. As shown in FIG. 9A,
 centering guides 148 and 150 include flanges 148A and 150A, respectively
 to ensure that the burnishing tape 126 is maintained centered on pad 106.
 The upper tape tracking assembly 144 and centering guides 148, 150 along
 with the arms 154, 156, and 158 are held in a fixed position, while
 carriage 114 with pad holder 110 is permitted to slide on rail 118 (not
 shown in FIG. 8).
 Take-up reel 134 with cover 134a is driven by motor 172. Supply reel 130
 with cover 130a is spring loaded to provide a desired amount of resistance
 when indexing the burnishing tape 126.
 FIG. 10 shows a cut-away side view of supply reel 130 with a spring loaded
 mechanism to provide resistance to the rotation of supply reel 130. Supply
 reel 130 is mounted on bearings 180a, 180b, and 182, which are mounted on
 axis 184. A spring 186 is pressed against supply reel 130 via a washer
 188. A nut 190 may be tightened on a bolt 192, which is coupled to axis
 184 to adjust the force with which spring 186 is pressed against supply
 reel 130. Washers 194 and 196 are used to center spring 186 on nut 190.
 Thus, by adjusting nut 190 the resistance in the rotation of supply reel
 130 may be adjusted to the desired amount, e.g., 100 grams.
 The force applied by tension spring 122 may be adjusted by adjusting the
 distance between the tension arms on the pad holders 110 and 112. Further,
 the tension on the burnishing tape 126 may be adjusted by altering the
 position of tape guides 146 and 152 relative to the position of the pads
 106 and 108. By moving tape guides 146 and 152 away from disk 101, tension
 on burnishing tape 126 will be increased, while moving tape guides 146 and
 152 towards disk 101 will decrease the tension on burnishing tape 126.
 The force applied by tension spring 122 and the tension on burnishing tape
 126 is calibrated by burnishing a test disk. Ink, e.g., from a felt tip
 marker, or some similar substance is applied to the test disk prior to
 burnishing the test disk. The ink is transferred to the burnishing tape
 during the burnishing process. Thus, by inspection of the burnishing tape
 after burnishing the marked test disk, one can determined whether the pad
 is square to the surface of the disk. A square pad print on the burnishing
 tape indicates that the pad is square to the disk.
 FIG. 11 shows a perspective view of a pad holder 210 in accordance with
 another embodiment of the present invention. Pad holder 210 is similar to
 pad holder 110 (FIG. 8) like designated elements being the same, however,
 pad holder 210 includes a main body 211 on which is mounted a removable
 tip 212. Tip 212 includes a depression 214 in which pad 106 is mounted.
 Tip 212 also includes a central orifice 213 that is aligned with orifice
 111 when tip 212 is mounted on pad holder 210.
 Tip 212 is mounted on body 211 of pad holder 210 with a bolt 215. The use
 of a removable tip 212 permits pad 106 to be replaced with a new pad
 without requiring the disassembly of burnishing apparatus 100.
 Advantageously, with the use of tip 212, pad 106 can be replaced by simply
 removing tip 212. A new pad may then be mounted on tip 212, which is then
 remounted on body 211 or a new tip, upon which a new pad is mounted, may
 then be mounted on body 211 of pad holder 210.
 FIGS. 12A and 12B show side and top views, respectively of pad holder 210.
 As shown in FIGS. 12A and 12B, tape guide rollers 146 and 152 include
 flanges 146A and 152A, which assist in maintaining the correct position of
 burnishing tape 126 (shown in FIGS. 3 and 4). Tape guide rollers 146 and
 152 are mounted on the body 211 of pad holder 210 via bolts 216 and 218,
 respectively, along with respective spacers 220 and 222. Spacers 220 and
 222 ensure that tape guide rollers 146 and 152 are at the correct position
 relative to pad 106 (shown in FIGS. 3 and 4) as well as permitting
 rotation of tape guide rollers 146 and 152. It should be understood that
 tape guide rollers 146 and 152 may be mounted on pad holder 110 (shown in
 FIGS. 3 and 4) in a similar manner.
 FIG. 13 is a perspective view of a burnishing apparatus 300 in accordance
 with another embodiment of the present invention. The pad holders on
 burnishing apparatus 300 are opposing scissor-like pad arms 302, on which
 are mounted burnishing pads 304. Burnishing apparatus 300 also includes
 swing arms 306, which provide tension on burnishing tape (not shown for
 the sake of clarity) when the tape is to be indexed. Burnishing apparatus
 300 also includes supply reels 310 and take-up reels 312, which are
 similar to the supply reels and take-up reels described above. A series of
 rollers 314, 316, 318, capstan rollers 320, 321 and index guides 322 are
 also included in burnishing apparatus 300. A base plate 324 is also
 provided, which advantageously separates motors (e.g., used with the
 take-up reels 312) and moving parts from the burnishing area near
 burnishing pads 302.
 Burnishing apparatus 300 operates in a manner similar to burnishing
 apparatus 100 described above. Burnishing apparatus 300, however, does not
 use pad holders that move on a linear slide rail, such as the type
 manufactured by Del-Tron part number 101x, but uses scissor-like pad arms
 302 as pad holders that have a rotational movement.
 FIGS. 14 and 15 are respective top plan and front views of opposing pad
 arms 302. Pad arms 302 are mounted on bearings 330 at approximately the
 center of mass. Pad arms 302 are preferably balanced at the point of
 rotation at bearings 330. Bearings 330 include a housing 332 that is
 attached to a pad arm plate 334 by pins and/or bolts 336 or any other
 appropriate method. Thus, pad arms 302 swing open and closed, i.e.,
 respectively away and towards each other, as indicated by arrows 338.
 Dead weights 340, shown in FIG. 15, are coupled to one end of pad arms 302
 via dead weight rollers 342, which are mounted on pad arm plate 334. Pad
 arm plate 334 is mounted above base plate 324 by a support 344. Dead
 weights 340 hang by a cable 341 below base plate 324, as shown in FIG. 15.
 Dead weights 340 bias pad arms 302 into a closed position, i.e., pads 304
 are biased together. Because pad arms 302 are balanced at the point of
 rotation at bearings 330, the force with which pads 304 are biased
 together can be carefully controlled. Thus, for example, a fifty gram dead
 weight 340 (including the weight of cable 341) will supply a 50 gram bias
 force on pads 304. When pad arms 302 are in a closed position, pads 304
 press a burnishing tape against the surfaces of a disk.
 Pad arms 302 also include extensions 346, which extend below pad arm plate
 334 through holes 347. Extensions 346 are used to open pad arms 302 and to
 permit pad arms 302 to close in a controlled fashion as will be described
 in more detail below in reference to FIG. 17. Extensions 346 may be
 integrally formed as part of arms 302 or may be a separate element that is
 mounted on arms 302.
 In one embodiment of the present invention, housing 332 may be adjusted
 inward and outward as indicated by arrows 331, for example by adjustment
 screws. Thus, distance between pad arms 302 may be adjusted to compensate
 for variations in the thickness of the disk being burnished, e.g., when
 different types of disks are being burnished. Further, if the size or
 shape of the burnishing pad 304 varies, the distance between pad arms 302
 may be adjusted accordingly. In another embodiment, both housings 332 may
 be placed on a linear slide and coupled together with a spring that
 provides less force than dead weights 340. Thus, arms 302 and pads 304
 will be automatically biased together to provide equal pressure on both
 sides of a disk and will be automatically centered on the disk.
 FIG. 16 shows a top plan view of one pad arm 302. Pad arm 302 includes a
 notch 350 at one end of the arm 302 into which a burnishing pad 304 is
 mounted. Notch 350 is approximately 0.3 inches deep. Burnishing pad 304 is
 mounted to pad arm 302 by inserting burnishing pad 304 into notch 350 and
 inserting a pin 351 (shown in FIG. 13) through the pad arm 302 and into
 burnishing pad 304. Thus, burnishing pad 304 may be easily replaced. Of
 course, if desired, burnishing pad 304 may be glued or otherwise mounted
 to pad arm 302. Notch 350 is at a small angle .theta., e.g., approximately
 two degrees, relative to perpendicular to pad arm 302. Consequently
 burnishing pad 304 is held at a small angle relative to perpendicular.
 Thus, when pad arm 302 is closed, the entire top surface of burnishing pad
 304 is pressed against the surface of a disk. A second notch 352 is
 located at the other end of pad arm 302 and is used to mount extension
 346.
 Pads 304 may be for example 0.46.times.0.4 inches and 3/16 inch thick. Pads
 304 may be manufactured from a material such as Poron 4701-40 from Western
 Rubber and Supply, located in Livermore, Calif.
 FIG. 17 shows a stepper motor 362 used to open and close pad arms 302. FIG.
 17 also shows a front view of pad arms 302 (similar to that shown in FIG.
 15) in broken lines and extensions 346. Stepper motor 362, which for
 example is manufactured by IMS, is mounted under base plate 324 on a mount
 plate 364. Stepper motor 362 drives a pair of screws 364 that are coupled
 to actuator arms 368 with nuts 370. Actuator arms 368 are mounted to base
 plate 324 at hinges 372.
 As shown in FIG. 17, the ends of actuator arms 368 contact extensions 346.
 Thus, to open pad arms 302, stepper motor 362 rotates screws 366 to force
 nuts 370 away from each other. Consequently, actuator arms 368 press
 inward on extensions 346. As extensions 346 are pressed toward each other,
 burnishing pads 304 at the end of pad arms 302 will be opened, i.e., moved
 away from each other. By reversing stepper motor 362, pad arms 302 may be
 closed. Because a stepper motor 362 is used, pad arms 302 are closed in a
 controlled fashion. Thus, the initial contact between the disk and the
 burnishing tape is gentle, which advantageously prevents damage to the
 disk.
 FIGS. 18 and 19 show a top plan view and a front end view, respectively, of
 swing arms 306 and the apparatus that rotates swing arms 306 to release
 and provide tension on the burnishing tape.
 Tape guides 382 and 384 are mounted on swing arms 306. Because the abrasive
 side of the burnishing tape will contact tape guide 382, tape guide 382 is
 a roller. Tape guide 384 only contacts the back side of the burnishing
 tape and therefore may be a pin. Swing arms 306 are mounted on a shaft 386
 that extends through bearings 388 and bearing housing 390. Bearing housing
 390 is mounted to base plate 324 by bolt 391. Shaft 386 extends through
 base plate 324 and is mounted to actuator arms 392. Actuator arms 392 are
 coupled to a linear actuator 394 via couplers 396, 398 and tie rods 399.
 Thus, as linear actuator 394 slides back and forth, actuator arms 392 will
 rotate shaft 386, which will rotate swing arms 306 as indicated by arrows
 307.
 FIGS. 20 and 21 show a simplified top plan view of burnishing apparatus 300
 in a closed and an open position, respectively. As shown in FIG. 20, a
 burnishing tape 301 extends from supply reel 310 between tape guides 382
 and 384 on swing arm 306 and around pad arm 302. In the closed position
 there is little or no tension on burnishing tape 301. The only tension on
 burnishing tape 301 required in the closed position is used to hold
 burnishing tape 301 in position on the various guides and rollers. The tip
 of pad arms 302 have a groove 303 (shown in FIG. 13) which helps center
 burnishing tape 301 over pads 304. Pads 304 press burnishing tape 301
 against the surfaces of disk 400. Burnishing tape 301 then extends over
 various rollers and guides which prevent burnishing tape 301 from
 contacting disk 400, except where pads 304 press burnishing tape 301
 against disk 400. Burnishing tape 301 is finally taken up at take-up reels
 312.
 FIG. 21 shows pad arms 302 in an open position with swing arms 306 in a
 position to provide tension on burnishing tape 301. With pad arms 302 in
 an open position, pads 304 are no longer pressing burnishing tape 301
 against the surfaces of disk 400. Thus, disk 400 may be replaced with a
 new disk to be burnished. Further, by rotating swing arms 306, tape guide
 382 applies tension to burnishing tape 301 such that burnishing tape 301
 is not in contact with pads 304. Consequently, burnishing tape 301 may be
 indexed to a new position without damaging pads 304.
 Burnishing tape 301 is indexed by capstan rollers 320 and 321 and the
 amount of indexing is detected by index guides 322. As shown in FIG. 13,
 index guides 322 include a sensor to indicate the precise amount that
 index guides 322 have moved. Thus, the amount burnishing tape 301 is
 indexed may be carefully controlled. If desired, burnishing tape 301 may
 be indexed by take-up reels 312. However, as burnishing tape 301 is taken
 up, the effective radius of the takeup reel 312 will change, making
 precise indexing of burnishing tape difficult.
 FIG. 22 shows a side view of a take-up reel 312. As can be seen, take-up
 reel 312 is mounted on a shaft 410 that is driven by a motor 412, such as
 a model number 3TK6GN-AUL motor manufactured by Oriental Motor or part
 number M409M378 manufactured by Globe Motor. Take-up reel 312 is permitted
 to slip on shaft 410. Thus, as the effect radius of the take-up reel 312
 changes due to the accumulation of burnishing tape 301 on take-up reel
 312, the amount that take-up reel 312 rotates does not need to be changed.
 FIGS. 23A and 23B show a front view and a side view of capstan rollers 320
 and 321, both sets, and the driving mechanism. A gearmotor 420, such as
 part number M409M378 manufactured by Globe Motor located in Dayton, Ohio,
 drives a belt (not shown) around two pulleys 422 and 424. Pulley 424
 drives both rollers 321 via gears 426 and 428.
 FIG. 24 is a side view of an index guide 322, which freely rotates, along
 with a sensor 430 used to detect the amount that index guide 322 has
 rotated and thus how much burnishing tape 301 has been indexed. Sensor 430
 may be, for example, may be the type manufactured by Omron located in
 Japan.
 Burnishing apparatus rotates disk 400 at a constant linear velocity (CLV),
 e.g., 300 meters/minute. The burnishing process is applied from the inside
 diameter to the outside diameter of disk 400. The desired burnish constant
 (K), which is e.g., 50, is controlled by the CLV and the time spent at
 each radial point. Thus, as is well understood by those skilled in the
 art, the burnishing apparatus 300 must have a differential traverse speed,
 which is specified by the burnish constant K. Of course, if desired the
 revolutions per minute (RPMs) of disk 400 may be held constant.
 While the present invention has been described in connection with specific
 embodiments, one of ordinary skill in the art will recognize that various
 substitutions, modifications and combinations of the embodiments may be
 made after having reviewed the present disclosure. The specific
 embodiments described above are illustrative only. Various adaptations and
 modifications may be made without departing from the scope of the
 invention. For example, various additional elements, such as sensors may
 be included in the burnishing apparatus. The spirit and scope of the
 appended claims should not be limited to the foregoing description.