News Column

Patent Issued for Adjustable Disk Stabilizer for a Spinstand

June 24, 2014



By a News Reporter-Staff News Editor at Journal of Technology -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Perevoztchikov, Konstantin (Saratoga, CA); Zhuang, Wei (San Francisco, CA); Guzik, Nahum (Mountain View, CA), filed on April 4, 2013, was published online on June 10, 2014.

The patent's assignee for patent number 8749917 is Guzik Technical Enterprises (Mountain View, CA).

News editors obtained the following quote from the background information supplied by the inventors: "Test devices known as spinstands are used to test and evaluate magnetic disks and magnetic heads used in hard disk drives, as well as other structural and functional components of drives. The disks generally include a relatively rigid disk having two parallel planar principle surfaces, and bearing a magnetic medium on at least one of the principle surfaces. In the spinstand, a spindle is driven by a motor to rotate about a disk axis, as data is written to and read from the disk, and evaluated. At such rotation rates, it is important to maintain mechanical stability of the disk, minimizing vibration, so that desired test procedures can be applied, and accurate testing measurements can be obtained.

"It also is important to be able to reconfigure a spinstand relatively quickly, for example, on a factory floor, so that various thickness magnetic media disks can be tested in succession on a given spinstand. For example, it may be necessary to analyze disks of a first thickness X, followed by disks of second thickness Y, followed by disks of a third thickness Z.

"In accordance with prior art, a disk-under-test is placed on a chuck and clamped by a chuck cap to the spindle. The spindle is driven to rotate about a spin axis of the spinstand by the drive motor.

"In conventional practice to maintain stability of a rotating disk on a spinstand, a plate having an at least 'nominally' flat bearing surface is disposed opposite and preferably parallel to the planar underside of the disk, maintaining a small gap G, between the bearing surface and the planar underside of the disk. Hard drives use a gap between 0.005 inch and 0.010 inch. Smaller gaps are harder to achieve in mass production and the spindle motor draws a lot of power with such gaps. As 'nominally' flat, the bearing surface may be smooth (for example, highly polished planar), or it may be textured, but is considered 'nominally' flat, or just 'flat' as used herein.

"With such a configuration, an air bearing is established between the planar underside of the disk-under-test and the bearing surface, providing a high degree of mechanical stability, minimizing vibration of the disk, during the test process. In accordance with conventional practice, a spinstand is set up to accommodate a disk of a given thickness so that the underside of the disk is opposite the bearing surface, with the bearing surface being parallel to the underside and with a desired gap G between the bearing surface and the underside of the disk.

"There are, however, at least two significant problems with such practice.

"First, it is very difficult, and time-consuming and thus costly, to establish such a parallel configuration for a first disk-under-test having a first thickness and/or diameter. Generally, in the prior art, a support structure for a given disk is typically composed of multiple elements, including shims, for fine adjustments.

"Second, when testing a succession of disks, after testing the first disk, the repetition of those alignment steps is required to establish a similar configuration for a second disk-under-test of a different thickness and/or diameter. Generally, in the prior art, in order to accommodate a succession of differing thickness and/or diameter disks, an entire assembly for supporting the plate having the bearing surface, must be reconfigured to accommodate the various thicknesses and/or diameter of the disks in the succession.

"In view of the need to continually develop equipment and methodologies suitable for effecting cost-efficient design and testing of magnetic read/write heads and disks, it is increasingly important to provide a solution to the above noted difficulties."

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "A spinstand is an instrument that is used for testing the characteristics of magnetic read/write heads and disks. The spinstand generally simulates the motions of the head with respect to a disk that occur in a hard disk drive. The spinstand includes a support and rotational driver for a magnetic disk-to-be-tested.

"An adjustable disk stabilizer for an exemplary spinstand is disclosed below where the spinstand includes a spindle motor and spindle assembly extending from a base, for supporting a disk in a disk locus extending transverse to and about a spindle axis. The disk typically has two mutually parallel planar annular principal surfaces, at least one of the principal surfaces bearing a magnetic medium. In a form, the disk is to be supported in the disk locus with the at least one of the magnetic medium-bearing principal surfaces facing away from the base. The spindle motor and spindle assembly spin the disk about the spindle axis at high speed.

"In a manner similar to the prior art, the disclosed configuration includes a plate, preferably having a 'nominally' flat (or just 'flat', as the term is used herein) bearing surface, with the bearing surface positioned opposite the underside of a disk-under-test and facing away from the base, during the testing/measurement process. In a form, the goal of that configuration is similar to that as discussed above in connection with the prior art, namely, to have the bearing surface of the plate parallel to, and separated by a small gap G from, the underside of the disk clamped by the chuck cap to the spindle in the disk locus, so that an air bearing is established by the undersurface of the rotating disk and the bearing surface opposite thereto.

"The disclosed adjustable disk stabilizer support structure for the disk stabilizer plate including the bearing surface, is significantly different from, and a substantial improvement over, prior art disk stabilizer support structures for disks on spinstands.

"In a form, the disclosed adjustable disk stabilizer support structure generally includes (i) a plate support element disposed about the spin axis and resiliently coupled to the base of the spinstand, and (ii) a selected disk stabilizer plate having a nominally flat, in some cases smooth planar, bearing surface and having an axial thickness related to the thickness of a disk-to-be-tested. When so configured, the plate support element has an upper surface facing the disk locus and extending perpendicular to the spin axis and about an end member of the spindle which is distal to the spindle motor. The selected disk stabilizer plate is affixed to that upper surface facing the disk locus, with its bearing surface facing the disk locus.

"In a form, the plate support element is resiliently coupled to the spinstand base by n alignment fasteners, such as cap screws, where each fastener extends from the plate support element, through a preloaded compression element (such as a compression washer, for example in the form of a Belleville washer), and engages a threaded hole in a structure rigidly coupled to the base of the spinstand. In a preferred form, n=3, but other numbers of fasteners can be used.

"In use, the fasteners resiliently coupling the plate support element to the base of the spinstand, are adjusted to establish compression of the compression elements, preferably at or near the middle of their adjustment range.

"For testing a disk-to-be-tested having a known/measured thickness, a disk stabilizer plate having a nominally flat or planar bearing surface, is selected for fixture to the planar upper surface of the plate support element. The disk stabilizer plate is selected to achieve desirable gap G between flat surface and the disk-under-test within adjustment range. The disk stabilizer plate is also selected for diameter, since in order to establish a stable air bearing between the underside of a disk-under-test and the bearing surface of the disk stabilizer plate, it is important the opposed surfaces are substantially matched in size.

"In a form, the disk stabilizer plate includes through-holes arranged so that when the disk stabilizer plate is affixed to the plate support element, as described, those through-holes permit access by a user to the alignment fasteners which resiliently couple the plate support element via the compression elements, to the spinstand base.

"The disk to-be-tested is then mounted to the end member of the spindle, and clamped to the spindle end member (for example, by a chuck cap similar to those used in spinstands of the prior art). The spindle, chuck and chuck cap establish for the media-bearing disk clamped thereto, that the mutually parallel principal surfaces of the disk are disposed perpendicular to the spindle axis.

"According to an aspect of the technology, of the various elements of the disclosed adjustable disk stabilizer assembly, only the bearing surface of the disk stabilizer plate needs to be machined or otherwise produced in a relatively high precision manner. The element-to-element surfaces of the disk stabilizer assembly can be produced in a relatively low precision manner. This important attribute of the disclosed adjustable disk stabilizer assembly is enabled by the selection of the thickness of the plate support element whereby, when the disk stabilizer plate is affixed to the plate support element, the bearing surface of the disk stabilizer is (i) approximately perpendicular to the spin axis, and (ii) positioned along the spin axis so that when the disk-to-be-tested is mounted to the spindle end member by the chuck assembly, the underside of the disk is separated from the bearing surface of the disk stabilizer by a gap G, as desired.

"Thus, the disclosed adjustable disk stabilizer is used to enable a simple user-adjustment (for example, requiring adjustment of only three cap screws using wrench W of FIG. 2) to the disk stabilizer plate to ensure that the bearing surface of the plate is parallel to the underside of the supported disk, as well as at a position along the spin axis so that a desired highly uniform gap G is established.

"As compared to the prior art configurations and methods, in a form, the simple adjustment of three cap screws to achieve proper alignment, is highly efficient and can be done in shorter period of time compared to prior art.

"Moreover, in order to test a disk of a second thickness and/or diameter after testing a disk of a first thickness and/or diameter, the operator merely has to remove the first disk, replace the disk stabilization plate with one corresponding to the thickness of the second disk to be tested, and/or diameter, and re-adjust the same three cap screws by an amount necessary for the media-bearing surface of the second disk to be at the desired offset from the reference plane, taking into account the thickness of the second disk. When so configured, testing of the disk may commence.

"Again, as compared to the prior art configurations and methods, the simple replacement of the top plate, adjustment of three cap screws to achieve proper alignment for testing a succession of disks of differing thicknesses and/or diameter, is highly efficient.

"These and various other features as well as advantages of present technology will be apparent upon reading of the following detailed description and review of associated drawings."

For additional information on this patent, see: Perevoztchikov, Konstantin; Zhuang, Wei; Guzik, Nahum. Adjustable Disk Stabilizer for a Spinstand. U.S. Patent Number 8749917, filed April 4, 2013, and published online on June 10, 2014. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=8749917.PN.&OS=PN/8749917RS=PN/8749917

Keywords for this news article include: Technology, Guzik Technical Enterprises.

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Source: Journal of Technology


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