DISK SWEEPER METHOD AND APPARATUS

Abstract: A removable cartridge (10, 20) having a magnetic disk (40) configured to reduce particulate contamination of the magnetic disk, the removable cartridge includes a top cartridge shell (60) and means (30) coupled to the top cartridge shell configured to reduce the particulate contamination of the magnetic disk, the means including a filtering material (31) and means configured to urge the filtering material to be in sliding contact with the magnetic disk while the magnetic disk is rotating at less than the operation speed.

Description: DISK SWEEPER METHOD AND APPARATUS This application claims the benefit and priority of Provisional Application Serial No. 60/107,859, filed November 9, 1998, which is herein incorporated by reference for all purposes. BACKGROUND OF THE INVENTION The present invention relates to increasing the reliability of storage media. In particular, the present invention relates to methods and apparatus for reducing particulate contamination in removable storage media. Particulate contamination has been discovered as a significant cause of failures of removable storage media, such as removable disk cartridges. Examples of such contaminants include dust, hair, organic compounds, food crumbs, smoke particles, and the like. These particles often cling to the surface of disks within disk cartridges and adhere to the surface, even when the disks are spinning around at the operating speed, for example 5000 rpm to 7500 rpm. Conventional storage habits contribute to particulate contamination. Removable disk cartridges are designed to be repeatedly inserted and removed from disk drives. When not in use, these disk cartridges are often stored on dusty shelves, in lint filled pockets, in piles next to computers, and the like. Seldom are disk cartridges returned to the relatively "clean" disk cartridge holders. This typical user behavior often causes a great number of particulate contaminants to adhere to the outside casing of these disk cartridges. When these disk cartridges are inserted into a disk drive, the particles are then introduced into the interior of the disk drive, and thus onto the disk itself. Particulate contamination can cause defects on the disk and cause irreversible disk drive hardware damage. As is known, conventional read/write heads that transfer data from disks are often very delicate and "fly" over the surface of the disk at a very low height. Contaminants on the surface of a disk that strike the read/write heads at the operating rpm are often sufficient to knock the read write heads out of alignment. As can be expected, the size of the contaminants that can cause such damage decreases as the physical size of the read/write head decreases and the data density of the disk cartridges increase. One previous method to reduce the number of particulate contaminants on a disk is found on conventional 3.5" floppy disks. This solution has been to provide a particulate trapping material (filter material) on at least one inner surface of a floppy disk. The filter material is typically in the same size and shape as the disk media. Because the disk media is flexible and undulates while being operated, the disk media often bends sufficiently to touch the filter material. The portion of the disk that touches the filter material thus has reduced particulate contamination. A further enhancement has been to force at least a portion of the filter material towards the disk so as to cause the filter material to touch the disk at particular locations. One drawback to these solution is that excessive amounts of filter material must be used. The filter material must be formed in substantially the same size and shape as the disk media because the locations where the disk media will bend and touch the filter material are unpredictable. The filter material is thus typically placed at all possible places the disk may bend and touch the filter material. Other drawbacks to these solutions include having a filter material in constant contact with the disk which may cause increased abrasion of the disk and increased torque required for the disk drive motor. As is expected, having the filter material in constant contact with the disk causes a physical drag on the rotation of the disk. To compensate for the increased drag, the torque provided by the drive motor of the disk drive must be increased, otherwise the disk drive motor may bum out prematurely. The increased torque requirement translates to a higher cost for the drive motor. Other drawbacks to these solutions include the increased abrasion and heating to the disk and subsequent effects on long term storage characteristics of the disk, and the like. What is thus required are improved methods and apparatus for reducing particulate contamination in removable disk cartridges without significant effects on drive performance. SUMMARY OF THE INVENTION The present invention relates to methods and apparatus for increasing reliability of removable storage media. In particular, the present invention relates to methods and apparatus for dynamically reducing particulate contaminants from magnetic disks. The apparatus may include at least one sweeper, but preferably, a first and a second sweeper. Each sweeper may slidingly engage a surface of the magnetic disk as the disk rotates at less than full operational speed. In some embodiments, the first and second sweepers can be coupled to a portion of a disk cartridge over the area to be swept. The sweepers can be placed at any location on the disk cartridge which allows the sweeper to contact the disk. Typically, the sweepers are positioned on the top and bottom portions of the disk cartridge, oppositely disposed from one another, such that the first sweeper contacts a top surface of the disk, while the second sweeper contacts a bottom surface of the disk. A filter material is disposed on a portion of the first and second sweepers, typically on a free end of the sweeper. The filter material may be formed in substantially the same size and shape as the sweepers, the size and shape being selected to provide the most efficient contact area for particulate removal. In some embodiments, a biasing mechanism is used to urge the sweepers away from the cartridge surface such that the filter material is forced against the disk surfaces. In yet other embodiments, a mechanism is provided for urging the sweepers away from the disk, such that the sliding contact between the filter material and the disk is removed. The above described embodiments are discussed in further detail below. By positioning the sweepers at specific locations on the disk cartridge, the locations on the disk where the filter material contacts the disk can be more accurately predicted. Accurately predicting the amount of filter material needed to sweep the disk surface reduces the amount of filter material used. Moreover, since the sweepers may be removed from constant contact with the disk, and since the filter material may only contact the disk at less than operational speed, the amount of abrasion to the disk, heating of the disk, and torque required of the disk drive motor, is also reduced. Thus, the present invention provides for reduced particulate contamination in removable disk cartridges without significant effects on drive performance. In one aspect of the present invention, a removable cartridge is provided having a magnetic disk. The removable disk includes a top cartridge shell having a surface and a first sweeper coupled to the top cartridge shell. To facilitate the sweeping of particulate contamination, the sweeper includes a filtering material. A biasing mechanism is also provided to urge the first sweeper away from the top cartridge surface to cause the filter material to be in sliding contact with the magnetic disk. In another embodiment of the invention, a removable cartridge is provided having a magnetic disk. The removable cartridge includes a top cartridge shell. Also included is a means coupled to the top cartridge shell for reducing the particulate contamination of the magnetic disk. The means includes a filtering material. A means is also provided for urging the filtering material into sliding contact with the magnetic disk while the magnetic disk is rotating at less than a predetermined speed. The predetermined speed is less than the operational speed of the disk. In yet another aspect of the present invention, a method is provided for reducing particulate contamination of a magnetic disk disposed in a removable cartridge. The method includes providing a removable cartridge having a particulate sweeper; accelerating the magnetic disk to an operational speed; and sweeping the particulate sweeper over the magnetic disk during the accelerating of the magnetic disk. Further understanding of the nature and advantages of the invention may be realized by reference to the remaining portions of the specification and drawings. BRIEF DESCRIPTION OF THE DRAWINGS In order to more fully understand the present invention, reference is made to the accompanying drawings. Understanding that these drawings are not to be considered limitations in the scope of the invention, the presently preferred embodiments and the presently understood best mode of the invention are described with additional detail through use of the accompanying drawings in which: Figs. 1 A and IB are a simplified illustration of an embodiment of the present invention; Figs. 2 and 2 A are simplified illustrations of a top view and a side view of a top sweeper according to an embodiment of the present invention; Fig. 2B is a simplified illustration of the filter; Fig. 3 illustrates an embodiment of a particulate trapping material; Figs. 4A and 4B are simplified illustrations of another embodiment of the present invention; Figs. 5A-5C a simplified illustrations of an overview of an embodiment of the present invention; and Fig. 6 illustrates a flowchart according to an embodiment of the present invention. DESCRIPTION OF THE SPECIFIC EMBODIMENTS Figs. 1 A and IB include a top view 10 and a side view 20, respectively, of an embodiment of the present invention. Top view 10 illustrates a top view of a top sweeper 30 relative to a magnetic disk 40 according to the present embodiment. Side view 20 illustrates a not to scale side view of top sweeper 30 and a bottom sweeper 40 positioned relative to magnetic disk 45 while magnetic disk 45 is rotating at less than the operational revolutions per minute (RPM). Side view 20 also illustrates a top shell 60 and a bottom shell 70 of the removable magnetic cartridge embodying the present invention. In the embodiment in Fig. IB, top sweeper 30 and bottom sweeper 40 are shown attached to an interior surface of a removable magnetic cartridge. Top sweeper 30 and bottom sweeper 40 are typically physically coupled to top shell 60 and bottom shell 70, respectively via an adhesive. Alternatively, or in addition, top sweeper 30 and bottom sweeper 40 may be coupled to the respective shells by any other conventional means such as adhesive, ultrasonic bonding, flattening of pins extending from the respective shells 31, 41, rivets, and the like. Typically, as shown, the sweepers span the width of the magnetic disk in order to reduce particulate contamination on both of the disk surfaces. Figs. 2, 2 A, and 2B illustrate a top view 100 and a side view 110 of a top sweeper according to an embodiment of the present invention. The sweeper is typically formed from a single piece of Mylar, Kapton, or a similar material having the illustrated geometry. The crosshatched regions 120 and 130 illustrate regions including a pressure sensitive adhesive (PSA). PSA region 130 may also be used in this embodiment to secure the sweeper to the shell, illustrated in Fig. IB, or the like. The sweeper may include registration holes 133 and 136. Registration pins extruded or molded integrally from a top or bottom shell may be used with these registration holes to properly position the sweeper relative to the magnetic disk. In one embodiment, after the registration pins extend through registration holes 133 and 136, the registration pins may be heated and flattened, as illustrated in Fig. IB. PSA region 120 provides a region where a particulate trapping material 120 may be affixed. In the present embodiment, a portion 160 of the sweeper is biased toward a disk in response to a pre-formed bend 170 in the sweeper. In operation, the amount of deflection by portion 160 in response to the sweeper being in contact with the disk is typically on the order of 3.1 millimeters for a top sweeper and 3.3 millimeters for the bottom sweeper. These deflections typically impart a drag upon the disk. The amount of total force or drag imparted by the top and bottom sweepers is typically less than 3% of the amount of torque provided by the spindle motor, when the spindle motor is at rest. Preferably the amount of force is typically less than 2% of the amount of spindle motor torque. As illustrated in Fig. 2, the top sweeper may include an opening 180 in the material. Opening 180 typically reduces the amount of force imparted by the sweeper onto the disk. Accordingly, the size and shape of opening 180 may vary significantly as shown in the Figures to achieve the desired force. Further discussion of the amount of force is discussed below. In the present embodiment, pre-formed bend 170 is shown approximately parallel to the edges of the sweeper. In other embodiments, pre-formed bend 170 need not be parallel, and pre-formed bend 170 may be at an angle relative to the edges. Typically, the angle should be significantly less than 90 degrees, and more preferably less than 45 degrees. Such alternative embodiments could provide a non-uniform sweeper pressure across the disk. A non-uniform pressure tends to promote a radial "sweeping" action on particles on the disk, either from the inner diameter towards the outer diameter, or from the outer diameter to the inner diameter. Particles therefore tend to be swept from the disk. In the present embodiment, for convenience only, the geometry of the bottom sweeper is substantially a mirror image of the top sweeper. However, as will be discussed below, typically the angle formed by the pre-formed bend in the bottom sweeper is smaller than the angle formed by the pre-formed bend in the top sweeper. Alternative embodiments of the present embodiment may have a substantially different shape depending upon the requirements. For example, as illustrated in the embodiments in inset 190 in Fig. 2B, the sweepers may include reverse bend region 190. In these embodiments, the reverse bend provides a lip-type end region that allows the disk to rotate in a direction opposite of the operating direction with reduced disturbance of the sweeper. Other sweeper shapes can be envisioned in light of the present invention disclosure to one of ordinary skill in the art. Other materials may also be used for the sweeper. Desired characteristics include a light-weight material that is durable. Further, it is desired that the sweeper material retain the configured shape so as to maintain roughly a uniform pressure between the sweeper and the disk at a particular disk rotation speed for a substantial part of the lifespan of the magnetic cartridge. In the present embodiment, as illustrated, the top sweeper includes a broad surface area region 300 with respect to the disk. When the disk rotates, an air current is formed in the vicinity of the disk surface that acts upon surface area region 300 to lighten the pressure applied by the sweepers onto the disk. In an embodiment of the present, when the disk is rotating at an operating speed, typically approximately 5400 rpms, the air current is sufficient to lift the top sweeper and the bottom sweeper from the surfaces of the disk. In embodiments of the present invention, the top sweeper and the bottom sweeper are lifted-off of the surface of the disk at lower numbers of rpms than the operating speed. For example, if the operating speed is 5400 rpm, the sweeper may lift off at approximately 4000 rpms and above, at approximately 3000 rpms and above, at approximately 2700 rpms and above, at approximately 2000 rpms and above, and the like. In other embodiments, the operating speed may be higher, for example 7200 rpms and the lift off speed may also be higher, for example, 6000 rpms. The speed of lift-off may be designed to be lower rather than higher in order to lessen the amount of abrasion between the sweepers and the disk and to lessen the amount of force required by the disk drive spindle motor to compensate for the sweeper friction. Fig. 3 illustrates an embodiment of a particulate trapping material. The material is embodied having the geometries illustrated to substantially conform to the shape of the sweeper. In embodiments of the present invention where the shape of the sweeper is different, the material may also have a different shape. Alternatively, the material may simply be rectangular. In the present embodiment, the type of material used is the same as the filter material found in present day 3.5" floppy disk drives. Other materials providing enhanced trapping ability, reduced abrasion, and the like could be selected for use by one of ordinary skill in the art in light of the present invention disclosure. Figs. 4A and 4B illustrate a top sweeper 400 in an unstressed state and a bottom sweeper 410 in an unstressed state relative to respective disk surfaces. In the present embodiment, the disk is disposed closer to the bottom shell than the top shell, thus to roughly equalize the amount of pressure provided by the top and the bottom sweepers, the angles of the sweepers relative to the shells is adjusted. As seen in Figs. 4A and 4B, the angle θb is typically greater than the angle θt. In operation, the amount of deflection of the top sweeper being in contact with the disk is typically on the order of approximately 3.1 millimeters. In operation the amount of deflection by the bottom sweeper being in contact with the disk is typically on the order of 3.3 millimeters. In an alternative embodiment θb may be substantially similar to θt, however the bottom sweeper may have a larger cut-out region. In this case, in operation the amount of force between the sweepers and the disk could still be approximately equal. In alternative embodiments of the present embodiment, the force between the sweepers and the disk need not be the same. Further, in alternative embodiments, the disk may be equidistant from the top and bottom shells. In such embodiments the amount of force between the sweepers and the disks may be similar or different. Figs. 5A-5C include a view 500 of a cartridge shell top, a view 510 of a cartridge shell bottom, and a view 520 of the shells superimposed upon each other, respectively. In this embodiment, a top sweeper is illustrated positioned within the top shell and a bottom sweeper is illustrated positioned within the bottom shell. Preferably, as shown in view 520, the top sweeper and the bottom sweeper typically both contact the disk at approximately opposite positions on the disk. In alternative embodiments, the locations of the sweepers need not be on opposite sides of the disk and may be positioned at any location on the cartridge shell where there is sufficient space. Further, in alternative embodiments of the present invention, the sweepers need not be positioned along the radial axis of the disk, as shown. Fig. 6 illustrates a flowchart according to an embodiment of the present invention. Initially a magnetic disk cartridge shell is provided, step 600. Next, the sweeper is provided with the particulate trapping material, step 610. The sweeper is attached to the cartridge shell in a conventional manner, for example, using methods described above, step 620. The magnetic disk is provided, and the magnetic disk cartridge is then assembled, step 630. When assembled, the sweeper is in contact with the surface of the magnetic disk. The magnetic disk cartridge may then be placed within a disk drive designed to access the cartridge, step 640. The magnetic disk is then accelerated, step 650. During acceleration, the sweeper begins to remove particulate contamination from the surface of the disk, step 660. When the magnetic disk approximately reaches a predetermined speed, the sweeper loses contact with the surface of the magnetic disk, step 670. The magnetic disk then reaches the operating speed, step 680. When the disk is to be removed, the rotation speed of the magnetic disk is reduced, step 690. The sweeper then re-contacts the surface of the magnetic disk to remove particulate contaminants, step 700. Finally, the heads are parked on the head load ramp, step 710. As described above, the p re-determined speed is fully configurable to any speed. For example, in the present embodiment, if the head is loaded onto the magnetic disk at a speed of approximately 2000 rpms, the sweeper may be designed to lift-off at approximately the same speed. Further, if the head is designed to be unloaded onto a head loading ramp at a speed of approximately 3000 rpms, the sweeper may be designed to re-contact the magnetic disk after the head is unloaded. Other lift-off or re-contact speeds are possible, depending upon other such factors. For example, a lower re-contact speed may be desired depending on emergency-power-off, and back EMF voltage considerations, and the like. In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. Many changes or modifications are readily envisioned. For example, the sweeper may include a plurality of contact regions or include a series of sweepers. Further, in some embodiments the upper and lower sweepers are not radially aligned. Moreover, the materials and the exact shapes of the sweepers may change according to particular product design considerations and product configuration. In one embodiment, the amount of force applied by the sweepers while at rest may vary substantially from the embodiment described above. For example, the sweeper may only be in contact the magnetic disk only before the magnetic heads are loaded onto the disk or only after the magnetic heads are unloaded from the disk. In another example, the sweeper may be in contact with the magnetic disk only when the disk is not at or above the operational number of rpms, and the like. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims.

Claims: WHAT IS CLAIMED IS: L A removable cartridge having a magnetic disk, the removable cartridge comprising: a top cartridge shell having a surface; a first sweeper coupled to the top cartridge shell, the sweeper including a filtering material; and a biasing mechanism to urge the first sweeper away from the top cartridge surface to cause the filter material to be in sliding contact with a magnetic disk. 2. A removable cartridge as in claim 1, wherein the filter material is in sliding contact with the magnetic disk while the magnetic disk is rotating in a predetermined range of speed. 3. A removable cartridge as in claim 2, wherein the range of predetermined speed is less than an operational speed of the disk. 4. A removable cartridge as in claim 1, further comprising: a bottom cartridge shell having a surface; a second sweeper coupled to the bottom cartridge shell, the second sweeper including the filtering material; and a biasing mechanism to urge the second sweeper away from the bottom cartridge surface to cause the filter material to be in sliding contact with the magnetic disk. 5. A removable cartridge as in claim 4, wherein the first sweeper and the second sweeper contact the disk at approximately opposite positions on the disk 6. A removable cartridge as in claim 1, wherein the sweeper material is taken from the group consisting of Mylar and Kapton. 7. A removable cartridge as in claim 1, wherein the biasing mechanism biases the first sweeper toward the magnetic disk in response to a pre-formed bend formed on a portion of the first sweeper. 8. A removable cartridge as in claim 1, wherein the first sweeper is deflected by the biasing mechanism to impart a force upon the disk, the force being less than 2% of the amount of torque used to rotate the disk. 9. A removable cartridge as in claim 8, wherein the amount of deflection in response to the first sweeper being in contact with the disk is about 3.1 mm. 10. A removable cartridge as in claim 1, wherein the first sweeper has a front edge, the front edge extending across substantially the radius of the magnetic disk. 11. A removable cartridge as in claim 1 , wherein the top sweeper has an opening which reduces the amount of force imparted by the first sweeper to the disk. 12. A removable cartridge having a magnetic disk, the removable cartridge comprising: a top cartridge shell; means coupled to the top cartridge shell for reducing the particulate contamination of the magnetic disk, the means including a filtering material; means for urging urge the filtering material to be in sliding contact with the magnetic disk while the magnetic disk is rotating at less than a predetermined speed, the predetermined speed less than the operational speed. 13. A method for reducing particulate contamination of a magnetic disk disposed in a removable cartridge, comprising: providing a removable cartridge having a particulate sweeper; accelerating the magnetic disk to an operational speed; and sweeping the particulate sweeper over the magnetic disk during the accelerating of the magnetic disk. 14 . A method as in claim 13, further comprising discontinuing the sweeping before the magnetic disk has reached the operational speed. 15. A method as in claim 13, wherein the sweeping comprises urging the sweeper into sliding contact with the magnetic disk. 16. A method as in claim 13, wherein the sweeper comprises: a first sweeper coupled to a top portion of the cartridge; and a second sweeper coupled to a bottom portion of the cartridge. 17. A method as in claim 16, wherein the first sweeper and the second sweeper contact the disk at approximately opposite positions on the disk. 18. A method as in claim 13, wherein the particulate sweeper material is taken form the group consisting of Mylar and Kapton. 19. A method as in claim 13, wherein the sweeper is biased during the sweeping to impart a force upon the magnetic disk, the force being less than 2% of the amount of torque used to rotate the disk. 20. A method as in claim 13, wherein the sweeper comprises a pre- formed bend formed on a portion of the sweeper.

Inventors: IFTIKAR SYED, MORRIS FRANK, NGUYEN LONG, TANNERT HANS, IFTIKAR, SYED, MORRIS, FRANK, NGUYEN, LONG, TANNERT, HANS
Applicants: CASTLEWOOD SYS INC, CASTLEWOOD SYSTEMS, INC.
Application year: 1999
Main classification: G11B23
IPC codes: G11B23