# Patent

## Title
Disk buffing apparatus with abrasive tape loading pad having a vibration absorbing layer

## Abstract

A disk buffing apparatus includes a spindle for rotating an annular disk, and a first pad arm for loading a first abrasive tape against a first surface of the annular disk. The first pad arm includes a pad arm frame having a pad receptacle and a first pad. The first pad has a first damping layer in contact with the first pad arm within the pad receptacle, and a first tape loading layer for contacting the first abrasive tape. The first damping layer comprises a first polymeric material and the first tape loading layer comprises a second polymeric material. The first polymeric material has a lesser hardness than the second polymeric material.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority to provisional U.S. Patent Application Ser. No. 61/833,904, filed on Jun. 11, 2013, which is hereby incorporated by reference in its entirety.


BACKGROUND
Information storage devices are used to retrieve and/or store data in computers and other consumer electronics devices. A disk drive is an example of an information storage device that includes one or more heads that can both read and write to a spinning disk media, but other information storage devices also include heads—sometimes including heads that cannot write.
The typical disk drive includes a head disk assembly (HDA) and a printed circuit board (PCB) attached to a disk drive base of the HDA. The HDA includes at least one disk (such as a magnetic disk, magneto-optical disk, or optical disk), a spindle motor for rotating the disk, and a head stack assembly (HSA). The spindle motor typically includes a rotating hub on which disks are mounted and clamped, a magnet attached to the hub, and a stator.
In magnetic recording applications, the disk includes a magnetic coating upon which the head performs read and write operations at a very close physical spacing. In optical and magneto-optical recording applications, the read head may include a mirror and an objective lens for focusing laser light on an adjacent disk surface.
In all of these applications, the flatness and smoothness of the disk is an important consideration. For example, in magnetic recording operations, the head must operate in very close proximity to the disk surface without frequent contact. The media layer of an optical disk may also have continuity and uniformity requirements that affect the specification of acceptable disk flatness and disk smoothness. Such specifications, in turn, can affect the requirements for manufacture of disks for information storage devices.
In certain disk manufacturing processes, a disk buffing apparatus is used to buff the surface of disks under manufacture with an abrasive tape, to thereby desirably affect disk surface characteristics. Conventionally, the disk buffing apparatus loads the abrasive tape on to the surface of the disk under manufacture by pressure applied through a tape loading pad.
However, a detrimental vibration is often observed, in which the tape and tape loading pad can bounce on the surface of the disk (e.g. a stick-slip phenomena) while the disk is spinning during the buffing process. Such vibration can be detrimental because if it is excessive then it can lead to degradation of the tape or disk surface quality and/or ultimately even undesired scratches on the disk surface. Thus, there is a need in the art for a disk buffing apparatus and method that can reduce undesired vibrations.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a perspective view of a disk buffing apparatus capable of including an embodiment of the present invention.
FIG. 2 is a perspective view of a region of a disk buffing apparatus, with abrasive tape supported by pad arms and tape guides, that is capable of including an embodiment of the present invention.
FIG. 3 is a perspective view of a region of a disk buffing apparatus, with pad arms, tape loading pads, and tape guides, capable of including an embodiment of the present invention.
FIG. 4 is a perspective view of a region of a disk buffing apparatus with pad arms and pad clamps, capable of including an embodiment of the present invention.
FIG. 5 is a perspective view of a pad arm clamping a tape loading pad that is capable of including an embodiment of the present invention.
FIG. 6 depicts a tape loading pad according to an embodiment of the present invention.



DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
FIG. 1 is a perspective view of a disk buffing apparatus 100 capable of including an embodiment of the present invention. In the embodiment of FIG. 1, the disk buffing apparatus 100 includes a spindle 110 for rotating an annular disk 112 about a spindle axis of rotation 116, and a first pad arm 120 for loading an abrasive tape against a first surface of the annular disk 112. The abrasive tape is not shown in the view of FIG. 1, because the abrasive tape is a disposable material that is used by the tape buffing apparatus 100, rather than being considered part of the disk buffing apparatus 100. However, in the embodiment of FIG. 1, the disk buffing apparatus 100 includes spools 130, 132 for storing and taking up the abrasive tape as it is being used.
In the embodiment of FIG. 1, the first pad arm 120 may include a pad arm frame 122 having a pad receptacle 124. The pad arm frame 122 may comprise aluminum or steel, for example. The disk buffing apparatus 100 may optionally also include a second pad arm 140, for loading an abrasive tape against an opposing second surface of the annular disk 112. The disk buffing apparatus may also include stepper motors 150, 152 that move the first pad arm 120 toward and/or away from the second pad arm 140, and in some embodiments, the second pad arm 140 toward and/or away from the first pad arm 120.
In the embodiment of FIG. 1, the tape buffing apparatus 100 further optionally includes a translation stage 114 that translates the spindle 110 in a direction normal to the axis of rotation 116, to change the buffing radius at which the abrasive tape is loaded against the surface of the disk 112. Preferably but not necessarily, an angular velocity of the spindle 110 is controlled to be inversely proportional to the buffing radius, so that the surface of the annular disk 112 will move relative to the abrasive tape at a constant linear velocity. In some embodiments, the linear velocity due to spindle rotation may preferably be in the range of 30 to 400 m/min at the buffing radius.
FIG. 2 is a perspective view of a region of a disk buffing apparatus 200, with an abrasive tape 210 and an abrasive tape 212. The abrasive tape 210 is stored and taken up by spools 230, 232 and the abrasive tape 210 is supported by a first pad arm 220 and by a tape guide 222. The abrasive tape 212 is stored or taken up by a spool 233, and the abrasive tape 212 is supported by a second pad arm 240 and by tape guides 242, 262, and 264. The abrasive tape 210 and the abrasive tape 212 may optionally include hard particles (e.g. alumina particles, diamond particles, or silicon oxide particles) adhered to a flexible polyethylene terephthalate tape substrate by an adhesive film. The first pad arm 220 and the second pad arm 240 are for loading the abrasive tapes 210 and 212 against opposing surfaces of an annular disk (e.g. annular disk 112 of FIG. 1).
FIG. 3 is a closer perspective view of a region of the disk buffing apparatus 200, in a non-operational state without abrasive tape. In the embodiment of FIG. 3, the first pad arm 220 includes the tape guide 222 and tape guides 266, 268. The second pad arm 240 includes the tape guides 242, 262, and 264. FIG. 3 also shows that the first pad arm 220 includes a first pad 270, and the second pad arm 240 includes a second pad 272. Preferably the structure of the first and second pads 270, 272 is the same.
FIG. 4 is a perspective view of the region of the disk buffing apparatus 200, in a non-operational state without abrasive tape, and with the tape guides and pads removed from the first and second pad arms 220, 240. In the embodiment of FIG. 4, the first pad arm 220 includes a first pad arm frame 221 that includes a pad receptacle 224. The second pad arm 240 includes a second pad arm frame 241 that also includes a pad receptacle (not visible in the view of FIG. 4). Preferably the structure of the second pad arm 240 is like that of the first pad arm 220. The pad receptacle 224 includes a pad clamp 402 that is forced into the pad receptacle 224 by a clamping spring 404. The function of the clamping spring 404 is better depicted in FIG. 5, which shows that the clamping spring 404 forces the pad clamp against a pad 270, and thereby clamps the pad 270 within the pad receptacle.
FIG. 6 depicts a pad 270 for abrasive tape loading, according to an embodiment of the present invention. In the embodiment of FIG. 6, the pad 270 has a damping layer 610 and a tape loading layer 620. Now referring to FIGS. 4-6, the damping layer 610 is in contact with the first pad arm 220, when the pad 270 is clamped within the pad receptacle 224 by the pad clamp 402. Now referring to FIGS. 2-6, the tape loading layer contacts the abrasive tape 210 and presses it against a surface of the annular disk being buffed (e.g. annular disk 112 of FIG. 1). In the embodiment of FIG. 6, the damping layer 610 comprises a first polymeric material and the tape loading layer 620 comprises a second polymeric material, and the first polymeric material has a lesser hardness than the second polymeric material.
In certain embodiments, the first polymeric material preferably comprises a polyurethane foam, and the second polymeric material optionally comprises a fluoro-elastomer. In certain embodiments the first polymeric material preferably has a hardness in the range of 2 to 40 Shore 0 Durometers and the second polymeric material optionally has a hardness in the range of 50 to 100 Shore A Durometers. In the embodiment of FIG. 6, a thickness t of the first damping layer is in the range of 10% to 30% of a combined thickness T of both the first damping layer and the first tape loading layer. In certain embodiments, the first polymeric material preferably has a bulk density in the range of 15 to 20 lb/ft3 and the second polymeric material optionally has a bulk density in the range of 109-119 lb/ft3. In certain embodiments, one or more of the foregoing geometry and/or material property ranges can advantageously reduce detrimental vibration in which the tape 210 and pad 270 can bounce on the surface of the disk (e.g. disk 112 of FIG. 1), and thereby reduce degradation of the tape or disk surface quality.
As can be understood by FIGS. 2-6, the first abrasive tape 210 and the second abrasive tape 212, and the annular disk (e.g. annular disk 112 of FIG. 1) may be all disposed between the first pad 270 and the second pad 272, and more specifically between the tape loading layer 620 of the first pad 270 and the tape loading layer of the second pad 272 (which faces the tape loading layer 620 of the first pad 270). Optionally, the first pad arm 220 may load the abrasive tape 210 against a surface of the annular disk with a first load force, and the second pad arm 240 may load the abrasive tape 212 against an opposing surface of the annular disk with a second load force that is approximately equal and opposite the first load force. The disk buffing apparatus may include one or more conventional load force transducers (e.g. load force transducer 430 of FIG. 4) that can sense the first load force and/or the second load force. In certain embodiments, the first load force and/or the second load force may preferably be in the range of 1 to 5 Newtons. In certain embodiments, a pressure between the abrasive tape 210 and the surface of the annular disk may preferably be in the range 1.5 to 8 N/cm2.
In the foregoing specification, the invention is described with reference to specific exemplary embodiments, but those skilled in the art will recognize that the invention is not limited to those. It is contemplated that various features and aspects of the invention may be used individually or jointly and possibly in a different environment or application. The specification and drawings are, accordingly, to be regarded as illustrative and exemplary rather than restrictive. For example, the word “preferably,” and the phrase “preferably but not necessarily,” are used synonymously herein to consistently include the meaning of “not necessarily” or optionally. “Comprising,” “including,” and “having,” are intended to be open-ended terms.

## Claims

1. A disk buffing apparatus comprising:
a spindle for rotating an annular disk;
a first pad arm for loading a first abrasive tape against a first surface of the annular disk, the first pad arm including
a pad arm frame having a pad receptacle, and
a first pad having
a first damping layer in contact with the first pad arm within the pad receptacle, and
a first tape loading layer for contacting the first abrasive tape;

wherein the first damping layer comprises a first polymeric material and the first tape loading layer comprises a second polymeric material, and the first polymeric material has a lesser hardness than the second polymeric material,
wherein the first and second polymeric material are configured such that the first pad dampens vibration, and
wherein a thickness of the first damping layer is in the range of 10% to 30% of a combined thickness of both the first damping layer and the first tape loading layer.

2. The disk buffing apparatus of claim 1 wherein the first polymeric material comprises a polyurethane foam.

3. The disk buffing apparatus of claim 1 wherein the second polymeric material comprises a fluoro-elastomer.

4. The disk buffing apparatus of claim 1 wherein the first polymeric material has a hardness in the range of 2 to 40 Shore O Durometers.

5. The disk buffing apparatus of claim 1 wherein the second polymeric material has a hardness in the range of 50 to 100 Shore A Durometers.

6. The disk buffing apparatus of claim 1 further comprising a first tape guide that guides the first abrasive tape from a first spool to the first tape loading layer.

7. The disk buffing apparatus of claim 1 wherein the first polymeric material has a bulk density in the range of 15 to 20 lb/ft3.

8. The disk buffing apparatus of claim 7 wherein the second polymeric material has a bulk density in the range of 109-119 lb/ft3.

9. The disk buffing apparatus of claim 1 further comprising a second pad arm for loading a second abrasive tape against a second surface of the annular disk, the second pad arm including a second pad that comprises a second damping layer in contact with the second pad arm, and a second tape loading layer for contacting the second abrasive tape, the second tape loading layer facing the first tape loading layer, wherein the second damping layer comprises the first polymeric material and the second tape loading layer comprises the second polymeric material.

10. The disk buffing apparatus of claim 9 wherein the first abrasive tape and the second abrasive tape and the annular disk are all disposed between the first and second tape loading layers.

11. The disk buffing apparatus of claim 9 wherein the first pad arm is movable towards the second pad arm, and the second pad arm is movable towards the first pad arm.

12. The disk buffing apparatus of claim 11 further comprising at least one stepper motor that moves the first pad arm towards the second pad arm.

13. The disk buffing apparatus of claim 11 wherein the first pad arm loads the first abrasive tape against the first surface of the annular disk with a first load force, and the second pad arm loads the second abrasive tape against the second surface of the annular disk with a second load force that is approximately equal and opposite the first load force.

14. The disk buffing apparatus of claim 13 further comprising a load force transducer that senses the first load force.

15. The disk buffing apparatus of claim 13 wherein the first load force is in the range of 1 to 5 Newtons.

16. The disk buffing apparatus of claim 9 further comprising a first tape guide that guides the first abrasive tape from a first spool to the first tape loading layer, and further comprising a second tape guide that guides the second abrasive tape from a second spool to the second tape loading layer.

17. The disk buffing apparatus of claim 1 wherein a pressure between the first abrasive tape and the first surface of the annular disk is in the range 1.5 to 8 N/cm2.

18. The disk buffing apparatus of claim 1 wherein the pad receptacle includes a pad clamp that is forced against the first pad by a clamping spring.

19. The disk buffing apparatus of claim 1 wherein the first abrasive tape is loaded against the first surface of the annular disk at a buffing radius, and wherein the first surface of the annular disk moves relative to the first abrasive tape at a constant linear velocity in the range of 30 to 400 m/min at the buffing radius due to spindle rotation.

20. The disk buffing apparatus of claim 19 wherein the spindle defines an axis of rotation, and further comprising a translation stage that translates the spindle in a direction normal to the axis of rotation to change the buffing radius, and wherein an angular velocity of the spindle is inversely proportional to buffing radius.