DISK DRIVE ASSEMBLY WITH VIBRATION DAMPENING CHARACTERISTICS

Abstract: A disk drive having vibration dampening elements and a method for dampening vibrations in disk drives. The disk drive includes a pivot assembly rotatably supporting an actuator assembly and a motor for rotating one or more disk-like recording media. One or more components of the pivot assembly and/or the motor have an elastomer-like compound molded to a portion thereof. The elastomer-like compound acts to reduce vibrations within the disk drive.

Description: DISK DRIVE ASSEMBLY WITH VIBRATION DAMPENING CHARACTERISTICS Field of the Invention The present invention relates to disk drives, more particularly to components for dampening vibrations in disk drives, and even more particularly to a disk drive having one or more components with an elastomeric- like compound molded thereto for dampening vibrations in the disk drive. Background of the Invention Disk drives of the type known as "Winchester" disk drives or hard disk drives are well known in the industry. Such disk drives are typically used in computer systems as mass storage devices to store recorded data. Such disk drives typically incorporate one or more rigid disks coated with a magnetizable medium, mounted for rotation at a constant high speed on the hub of a brushless DC spindle motor. Data is recorded to and read from a plurality of concentric, circular tracks on the disks by an array of read/write heads. These heads are incorporated in slider assemblies which interact with the air pulled along by the spinning disks to "fly" the heads in close proximity to the disk surface. The heads are typically moved radially from track to track on the disks by an actuator assembly. A typical actuator assembly includes an . actuator motor, a guidance mechanism to control the path of motion of the heads and support mechanisms to attach the heads to the moving actuator and support the heads in correct relationship to the disks. Advances in disk drive technology have revolved around reducing the size of disk drive components and the size of the overall disk drive. Smaller disk drives can allow for a reduction in the overall size of the computer system into which the disk drives are installed. With the reduction in the size of the disk drive, more space is available within the computer system for other components. In addition to the small disk drives, the disk drive industry has also made advances toward increasing the storage capacity of individual disk drive units. This increase in capacity has been brought about by increases in the linear density and track density of the disks. Linear density refers to the amount of data recorded along a given length of track. Increases in linear density have been brought about, at least in part, by improvements in heads, media and data encoding schemes. Track density refers to the number of data tracks recorded .across a given radial distance on the disk. Increases in track density have been brought about, at least in part, by improvements in heads, media, actuator motors and the servo systems used to precisely locate the heads relative to the tracks. The reduction in size of the disk drive can compound certain problems often associated with various operational features of disk drives. One such problem involves vibrations or harmonic oscillations in the disk drive. All disk drives experience a level of vibration or harmonic oscillations from various moving parts or electronic switching from within the disk drive or from the computer system. The effect of vibrations and oscillations has become magnified as the size of the drive is reduced and data tracks are spaced closer together. As a result, the overall performance of the drive is negatively impacted. In response to this problem, a number of solutions have been investigated which employ the use of elastomers within the disk drive for vibration dampening. U.S. Patent No. 4,896,239 discloses the use of an elastomeric O-ring in a stepper motor used to drive the carriage that supports the heads in a disc drive. The elastomeric O-ring is injected into annular channels formed in the stepper motor housing at locations opposite the outer diameter of the ball bearings that support the stepper motor shaft. The O-ring of elastomeric material acts to prevent radial deflection of the stepper motor shaft due to vibration or changes in the loads applied to the stepper motor shaft. However, the O-ring is not disclosed as being molded to any discrete component within the stepper motor, as taught by the present invention, and is pliant to allow movement in the axial direction but rigid to prevent movement in the radial direction of the stepper motor shaft. This elastomeric O-ring is not capable of reducing vibration levels to currently desired levels in disk drives, for example, which employ voice coil motors to drive the actuator mechanism. U.S. Patent 5,365,388 discloses an O-ring and gasket of urethane. The O-ring is a separate component placed between the stator and the shaft to keep the stator in proper relation to the shaft and to absorb vibrations. The patent also employs a gasket of urethane between the stator and the circuit board to absorb vibrations from the stator. Again, the vibration dampening means is not molded to a component within the disk drive and has failed to reduce vibration levels within the disk drive to desired levels. U.S. Patent 4,598,328 discloses a mechanical damper for disk drives having a band drive actuator. The damper comprises a elastomeric member in the form of a sleeve portion placed over the end of and coupling an inertial mass to the motor drive shaft. However, this dampening means does not include an elastomer-like material molded onto a component in the disk drive and has failed to reduce vibration within the disk drive to desired levels. U.S. Patent 5,136,450 discloses a laminate sleeve disposed between the spindle hub and the disks of a disk drive for reducing radial disk displacement relative to the spindle hub due to differential thermal expansion between the spindle hub and the disks. The sleeve is formed from a first layer of polytetrafluoroethylene, a second layer of a polyamide resin and a third laminating adhesive layer bonding the first two layers together. However, the sleeve does not act to dampen vibrations, but rather allows for differential thermal expansion between components of differing materials. Further, the sleeve is a separate component and is not molded to another component in the disk drive. Accordingly, there is a need for a disk drive assembly exhibiting improved vibration dampening characteristics. Summary of the Invention The present invention satisfies this need by providing a disk drive assembly having vibration dampening elements and a method for dampening vibrations in disk drives. The present disk drive includes a pivot assembly and a motor. At least one elastomer-like material or compound is molded to one or more portions of the pivot assembly, the motor or both by a molding process so as to improve vibration dampening characteristics in the disk drive assembly. The elastomer-like compound acts to reduce vibrations within the disk drive. In accordance with one aspect of the present invention, a disk drive assembly is provide which comprises a plurality of disk drive components including at least one head for recording and/or reading information on one or more disk-like recording media. A typical disk-like recording medium includes a plurality of circular, concentric tracks and may be of the type used in hard disk drives or so-called floppy drives. The head is supported for movement from track to track by an actuator assembly. The pivot assembly rotatably supports the actuator assembly for radial movement with respect to the recording medium. The motor can be any type, such as a spindle motor, suitable for rotating the disk-like recording medium. The disk drive components can be housed in some form of an enclosure. It is desirable for the enclosure to be sealed. The pivot assembly may include one or more of a pivot shaft, one or more pivot bearings disposed between the pivot shaft and the actuator assembly, and a pivot housing disposed between the at least one pivot bearing and the actuator assembly. The pivot bearing supports the pivot housing on the pivot shaft. Before these pivot assembly components are assembled in the disk drive, one or more elastomer-like compounds may be molded to a surface on the pivot shaft, the pivot housing, one or more pivot bearings or a combination thereof. For example, it may be desirable for one or more elastomer-like compounds to be molded to at least a portion of an outer diameter of the pivot shaft; an inner and/or outer diameter of one or more of the pivot bearings; an inner diameter of the pivot housing; or a combination thereof. When molded thereto, it is more desirable for substantially all of the inner diameter and/or substantially all of the outer diameter to be molded with an elastomer-like compound. The spindle motor may include one or more of a motor spindle shaft supporting the rotation of one or more disk-like recording media, at least one spindle bearing disposed between the motor shaft and one or more disk-like recording media, and a motor stator operatively adapted to rotate one or more disk-like recording media, for example, by cooperating with a motor hub mounted on the motor shaft. Before these motor components are assembled in the disk drive, one or more elastomer-like compounds may be molded to a surface on the motor shaft, one or more spindle bearings, the motor stator or a combination thereof. For example, it may be desirable for one or more elastomer-like compounds to be molded to the motor shaft so as to be disposed between the motor shaft and the motor hub. For example, at least two molded sections of one or more elastomer-like compounds can be disposed axially apart on the motor shaft. Alternatively, one or more elastomer-like compounds can be on the motor shaft in the form of a molded body section of generally uniform thickness. Two such spaced apart molded sections and one such uniformly thick molded body section can also be molded together onto the motor shaft, with the molded body section being thinner than and disposed between the two molded sections. It may also be desirable, for example, for one or more elastomer-like compounds to be molded to an inner and/or outer diameter of one or more spindle bearings. It may further be desirable for one or more elastomer-like compounds to be molded to one or more of an upper surface, a lower surface, an interior diameter surface and an outer diameter surface of the motor stator. For example, if the motor stator includes a series of stator poles disposed along either its interior diameter or its outer diameter, the one or more elastomer-like compounds can be molded to the outer diameter or interior diameter, respectively (i.e., to whichever diameter of the stator the stator poles are not disposed) . In either case, it may be desirable for one or more elastomer-like compounds to be molded to the upper surface and/or the lower surface. It may be desirable for an elastomeric-like compound to be molded to each of the pivot shaft, the pivot bearing(s), the pivot housing, the motor spindle shaft, the spindle bearing(s) and the motor stator. Each elastomer-like compound is chemically bonded and/or mechanically bonded to the surface being molded. It may be desirable for the surface on which an elastomer-like compound is molded to be a primed surface and/or a textured surface. In accordance with another aspect of the present invention, a method is provided for improving vibration dampening characteristics in disk drives. The method includes the step providing a disk drive assembly having a plurality of disk drive components including at least one disk-like recording medium, at least one head for at least one of recording and reading information on the at least one recording medium, an actuator assembly supporting the head, a pivot assembly rotatably supporting the actuator assembly and a motor for rotating the recording medium. One or the other or both of the motor and the pivot assembly have at least one surface with one or more elastomer-like compounds molded thereto. The elastomer-like compound is selected so as to be suitable for dampening undesirable vibrations within the disk drive assembly. The selection can be based upon any undesirable resonant frequency or frequencies present in the disk drive assembly when built without the elastomer-like compound. Other factors determining the compound(s) selected can include hardness, allowed dimensional limits within the disk drive assembly and other criteria known in the art. The elastomer-like compound is molded to at least a portion of the motor and/or the pivot assembly using any suitable molding technique so as to chemically bond and/or mechanically bond the elastomer-like compound to the disk drive portion. Exemplary molding techniques include, for example, at least one of transfer molding, injection molding, compression molding and like molding. It is desirable for each of the motor stator, the spindle bearing(s), the motor spindle shaft, the pivot shaft, the pivot bearing(s) and the pivot housing to have an elastomer-like compound molded thereto. After being molded with one or more elastomer¬ like compounds, the portion of the motor and/or the pivot assembly is assembled into the disk drive assembly. Before the molding step, it may be desirable to clean or otherwise remove contaminates from the surface to be molded. It may also be desirable for the surface to be molded to have a primer applied and/or to be roughened or otherwise textured before the molding step. After the molding step, the elastomer-like compound and disk drive portion on which it is molded are baked to improve the properties of the elastomer¬ like compound. Accordingly, it is an object of the present invention to provide a disk drive with reduced acoustic noise levels due to the reduction of specific vibrations within the disk drive. It is another object of the invention to provide a disk drive with improved data track following capability due to the reduction of vibrations within the disk drive. It is an additional object of the invention to provide a vibration dampening elastomer-like compound in a disk drive that is not subject to substantial outgassing over the expected internal temperature range of the disk drive. It is also an object of the invention to provide a vibration dampening elastomer-like compound in a disk drive that maintains its dampening characteristics over the expected internal temperature range of the disk drive. It is a further object of the present invention to provide a disk drive assembly that embodies lower vibration without creating more difficult assembly and without increasing parts count. These and other objects, and the features and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings and the appended claims. Brief Description of the Drawings Figure 1 is an exploded perspective view of a disk drive assembly in which the principles of the present invention are particularly useful. Figure 2A is an exploded perspective view of one pivot assembly of the present invention including an elastomer-like compound molded to a pivot shaft and two pivot bearings. Figure 2B is a cross-sectional side view of a pivot housing according to the present invention having an elastomer-like compound molded to an inner diameter thereof. Figures 3A and 3B are perspective views of a first and second embodiment of a motor stator according to the present invention with an elastomer-like compound molded thereto. Figure 3C is a plan view of the motor stator of Figure 3A without the elastomer-like compound molded thereto. Figures 4A, 4B and 4C are perspective views of alternative embodiments of a motor spindle shaft according to the present invention with an elastomer¬ like compound molded thereto. Detailed Description of the Invention The present invention relates to a disk drive assembly having vibration dampening components and to a method for dampening vibrations in disk drives. Disk drives experience resonant vibrations due to, for example, movement of various mechanical components within the disk drive and the switching of certain electronic signals in the disk drive or the computer system. In order to assure proper operation of the disk drive, these vibrations must be minimized. The effect of vibrations and oscillations becomes magnified as the size of the drive is reduced and data tracks are spaced closer together. For example, as disk drive actuators become faster, the components of the actuator system and the support mechanism for the heads tend to be mechanically excited by rapid acceleration and deceleration when the heads are moved from track to track. The recording or recovery of data on the disks can only be accomplished if the heads are stable relative to the data tracks. However, if the heads are oscillating at the natural frequency of the actuator/head subassembly, this oscillation can result in the heads moving back and forth about the desired track center to such an extent as to inhibit reliable data transfer. Similarly, the electronic switching of the commutation signals used to drive the spindle motor can result in stimulation of the spindle motor stator structure and sympathetic vibration of the disk drive housing, resulting in unwanted acoustic noise or the transfer of vibration to the critical head positioning mechanisms. As a result, the overall performance of the drive is negatively impacted. The present invention employs the dampening abilities of elastomer or elastomer-like materials to at least minimize to a significant degree, if not eliminate, undesirable vibrations. The present invention will now be described with reference to the particular embodiments shown in the figures. It will be recognized by one of ordinary skill in the art that the present invention can apply to various styles or designs of disk drives including, for example, various hard disk drives, to those utilizing Winchester technology, and to so-called floppy disk drives. In addition, it will be recognized by one of ordinary skill in the art that other types of disk drives such as, for example, optical disk drives employing laser read/write technology may also benefit from the present invention. It will also be recognized that the disk drive depicted in the figures is employed for exemplary purposes only. Referring to Fig. 1, there is seen a disk drive assembly 10 of the type in which the present invention is particularly useful. Disk drive assembly 10 includes a lower housing 12 and a top cover or upper housing 14, which together form an enclosure. It is desirable for the enclosure to be sealed. The components of the disk drive assembly 10 are directly or indirectly mounted onto the lower housing 12. Upper housing 14 encloses the internal components of the disk drive assembly 10 to protect the components from external contaminants or other damage. Disk drive assembly 10 includes a printed circuit board 16 and is mounted in a computer system (not shown) for operation of disk drive assembly 10, as is well known in the art. Disk drive assembly 10 also includes at least one magnetic or optical recording medium or disk 18 for recording and storing information, as is well known in the art. Disk 18 is rotatably mounted to lower housing 12 via motor spindle shaft 20 and motor rotor or hub 22. Motor spindle hub 22 supports disk 18 while motor spindle shaft 20 rotates in response to a sequence of timed, polarity-controlled commutation pulses generated by electronic logic on printed circuit board 16. These commutation pulses, when passed through stator windings 35 (See Figure 3C) , create magnetic fields which interact with the magnetic field of a plurality of permanent magnets (not shown) mounted in the motor hub 22, in a manner well known to those of skill in the art, to rotate the motor hub 22 at a closely regulated high speed.. Thus, motor hub 22 and stator 24 form a motor 23. While the motor 23 depicted is of the type know as a "stationary shaft motor", it will be recognized by one of ordinary skill in the art that other motors, such as "rotating shaft motors" in which the motor spindle shaft 20 rotates in conjunction with the motor hub 22, are within the scope of the present invention. Disk 18 is secured to motor hub 22 via a retaining ring 26 or other means well known in the art. Disk drive assembly 10 may included two or more disks 18 as is common in the art. When more than one disk 18 is employed, the numerous disks 18 may be separated by means of spacers 28, as is well known in the art. To provide smooth rotation of motor hub 22 and to maintain proper alignment, at least one spindle bearing 30 may be employed between motor spindle shaft 20 and motor hub 22 as is well known in the art. It is desirable for two or more bearings 30 to be employed in multiple locations between motor spindle shaft 20 and motor hub 22. Each of the bearings 30 may be any suitable bearing known in the art such as ball or roller bearings. Stator 24 is mounted to the lower housing 12 in a recess 32. Stator 24 may be any stator as is well known in the art. Stator 24 may be formed integrally with the stationary motor spindle shaft 20 or as separate components as shown. In addition, stator 24 includes a number of stator poles 34, wrapped with stator windings 35, as shown in Fig. 3C. Stator poles 34 include stator windings 35 and are separated from one another by stator openings 36. Stator poles 34 may be disposed along the surface of the interior diameter 38 of stator 24 as shown in Figs. 3A, 3B and 3C or along the surface of the outer diameter 40 (not shown) . In addition, stator 24 may include a connector 42 for connecting stator 24 to printed circuit board 16. Returning to Figure 1, disk drive assembly 10 also includes an actuator assembly 44. Actuator assembly 44 includes an actuator arm 46 for supporting read/write heads 48. Heads 48 allow information to be recorded or retrieved from the disk-like recording media 18. Read/write heads 48 are connected to the printed circuit board 16 via an electrical connector 50. Actuator arm 48 is adapted for movement over the disk¬ like recording medium 18 to allow information to be recorded and stored in the proper location. The movement of actuator arm 46 is controlled by voice coil motor 52. Voice coil motor 52 generally comprises a motor coil 47 on the actuator arm 46. When the disk drive is assembled, the motor coil 47 is located within the field of a pair of permanent magnets 54 and 56. Controlled DC currents, generated on printed circuit board 16 and passed through the motor coil 47 generate magnetic fields which interact with the magnetic fields of the permanent magnets 54 and 56 to move the motor coil 47 in accordance with the well known Lorentz relationship. Actuator assembly 44 also includes a pivot member or shaft 58 which rotatably supports actuator arm 46 via pivot housing 62. To provide smooth rotation of the actuator arm 46 and to keep pivot shaft 58 properly centered, actuator assembly 44 may also include at least one pivot bearing 60 and desirably at least two pivot bearings 60. Each of the pivot bearings 60 is disposed between the pivot member 58 and the pivot housing 62. Each pivot bearing 60 may be any suitable bearing known in the art including ball and roller bearings. Pivot shaft 58 and bearings 60 are enclosed and protected by the pivot housing 62. Pivot housing 62 may be an integral part of the actuator arm 46 or form a separate element as shown. Of course, one of ordinary skill in the art will recognize that the above-described disk drive is a representative example only and the present invention is not intended to be limited to any specific type of disk drive. Other examples of suitable disk drives useful in the present invention U.S. Patent No. 5,029,026 to Stefansky et al and U.S. Patent No. 4,870,703 to Augeri et al, the disclosures of which are both incorporated herein by reference in their entirety. The present invention also comprises a method of dampening disk drives and of providing a disk drive which has an elastomer-like compound molded to various elements within the disk drive assembly. The components of the exemplary disk drive assembly 10 to which the elastomer-like compound will be molded include the motor stator 24, the motor spindle shaft 20, the spindle bearings 30 supporting the motor spindle shaft 20, the pivot shaft 58 of the actuator assembly 44, the pivot bearings 60 and the pivot housing 62. At least one of the above mentioned components molded with an elastomer¬ like compound is employed in the present invention. However, any multiple of the above mentioned components may be employed. In particular, employing an elastomer¬ like compound on both the pivot shaft 58 and the motor stator 24 is desired. It is more desirable for each of the pivot shaft 58, the motor 23 and the motor spindle shaft 20 to have an elastomer-like compound molded thereto. Turning now to Fig. 2A, there is seen the pivot member 58, pivot bearings 60 and pivot housing 62 according to the present invention. At least one of the pivot shaft 58, the pivot bearings 60 or the pivot housing 62 includes an elastomer-like material molded thereto. Pivot shaft 58 preferably includes an elastomer-like material 64 molded to the outer diameter of pivot shaft 58. Elastomer-material 64 may be molded to all or any smaller portion of the axial length of the pivot shaft 58. In other words, the entire outer diameter of pivot shaft 58 need not be molded with elastomer-like material 64. Rather, the elastomer-like compound can be molded to a smaller portion of the outer diameter at the intended location of the pivot bearings 60. It is desirable for the elastomer-like material 64 to be molded to substantially the entire outer diameter of pivot shaft 58. Pivot shaft 58 may include a lower lip 66, extending horizontally a distance from pivot shaft 58. In such cases, elastomer-like material 64 may also be molded to the upper surface 68 of lower lip 66. Elastomer-like material 64 acts as a dampener, absorber or minimizer of vibrations or shocks that would otherwise be transferred from the pivot shaft 58 to the actuator arm 46 and thereby read/write heads 48. In addition, the pivot bearings 60, supporting the pivot housing 62, may also have an elastomer-like material molded thereto. The pivot bearings 60 include an outer diameter 70 and an inner diameter 72. Elastomer-like material 64 may be molded to either the inner diameter 72, the outer diameter 70 or both. It is desirable for the elastomer-like material 64 to be molded on the inner diameter 72. In fact, if desired, elastomer-like material 64 may be molded on the inner diameter 72 of the bearings 60 in conjunction with or in lieu of elastomer-like material 64 being molded on the pivot shaft 58. The spindle bearings 30, as shown in Fig. 1, support the motor spindle shaft 20. An elastomer-like material 64 may be molded to the spindle bearings 30 in the same way as that shown and described above for the pivot bearings 60 (see Fig. 2A) . Referring to Fig. 2B,the pivot housing 62 may also include an elastomer-like material molded thereto. The housing 62 includes an outer diameter 63 and an inner diameter 65. Elastomer-like material 64 may be molded to the inner diameter 65. It is desirable for substantially all of the inner diameter 65 to have the elastomer-like material 64 molded thereto. However, the elastomer-like material 64 may be molded to any appropriately lesser portion thereof. Turning now to Figs. 3A - 3C, and in particular Figures 3A and 3B, there is seen the motor stator 24 of the present invention having an elastomer¬ like material 64 molded thereto. The motor stator 24 may be of the kind having stator poles 34 disposed on its inner diameter 38, as shown in Figs. 3A - 3C, or having stator poles 34 disposed on its outer diameter 40 (not shown) , as is known in the art, or of any other type known in the art, including both rotating shaft and stationary shaft type motors. Referring to Fig. 3C, there is seen a motor stator 24 for motor 23 without the elastomer-like material 64 molded thereto. Motor 23 may include a motor stator 24, stator poles 34, stator openings 36, an outer stator diameter 40, an inner stator diameter 38, an upper stator surface 74 and a lower stator surface 76. As seen in Fig. 3A, elastomer-like material 64 may be molded to encapsulate stator 24 by having elastomer¬ like material molded to the outer diameter 40, upper surface 74, lower surface 76 or any combination thereof. It is desirable for the elastomer-like material 64 to be molded so as not to cover the stator poles 34. Therefore, when the stator poles 34 are disposed on the outer diameter 40 of stator 24, it is desirable for the elastomer-like material to be molded on the inner diameter 38 and not the outer diameter 40. - 17- Alternatively, elastomer-like material 64 may be molded to only the outer diameter 40 as shown in Fig. 3B or to the upper or lower surfaces, 74 and 76, respectively, depending upon the desired application. If stator poles 34 are provided on outer diameter 40 (not shown) , then elastomer-like material may be molded to the inner diameter 38, upper surface 74, lower surface 76 or any appropriately lesser combination thereof. Turning now to Figs. 4A-4C, there is seen three embodiments of a motor spindle shaft 20 having an elastomer-like material 64 molded thereto according to the present invention. Elastomer-like material 64 may be molded to all or any portion thereof of motor spindle shaft 20. As can be seen in Fig. 4A, elastomer-like material 64 may be molded to the motor spindle shaft 20 in at least one molded section such as, for example, a dual ring-like arrangement 78, with one molded section 78 being disposed at each end of the shaft 20. Alternatively, elastomer-like material 64 may be molded to the motor spindle shaft 20 in two spaced apart ring¬ like sections 78 and a molded body section such as, for example, a blanket arrangement 80 disposed between the ring-like sections 78 as shown in Fig. 4B. In this embodiment, the blanket section 80 is a thinner layer of elastomer-like material than the ring-like sections 78. As another alternative, elastomer-like material 64 may be molded to motor spindle shaft 20 in only a blanket arrangement 82 of substantially uniform thickness as shown in Fig. 4C. The apparatus and method of the present invention comprise molding an elastomer or elastomer¬ like compound to various components of a disk drive to reduce vibrations within the drive. Because it is molded to the disk drive component, the elastomer-like material is mechanically and/or chemically bonded to the surface on which it is molded. In addition to the selection of elastomers for vibration dampening, there are other factors to be considered when selecting materials for inclusion in a disk drive, especially when the housing is sealed. One of these factors is referred to as "outgassing", or the tendency of some materials to release molecules into the air within the sealed environment. Such molecules can accumulate on the surfaces of the disks or head sliders and lead to the deterioration of the critical hydrodynamic relationship between the heads and disks. This is especially important in current generations of disk drives where the heads are designed to "fly" at heights above the disk surface of only 1.5 to 2 microinches (3.8 to 5.1 microcentimeters) . Furthermore, current disk drives are typically specified to operate over ambient temperature ranges of, for instance, from 0°C to 40°C. Such an operating temperature range for the disk drive itself means that internal components, such as elastomer-like compounds suitable for the present invention, are subjected to much greater temperature variation. Thus, the selected elastomer must not outgas over this entire temperature range, and also must retain its dampening characteristics over this temperature range as well. The materials useful in the present invention include elastomers and compounds which possess elastomer-like properties. Elastomers are generally characterized as all substances having the properties of natural, reclaimed, vulcanized or synthetic rubber. Those properties include but are not limited to the abilities to stretch under tension, to have a high tensile strength, to retract rapidly after deformation, and to recover fully to the original dimensions. Thus, almost any compound displaying these properties may be employed in the present invention. The present invention envisions that the selection of an elastomer-like compound will be made with foreknowledge of an existing undesirable vibration frequency in the disk drive, and should include criteria relating to the material's lack of outgassing and ability to maintain its dampening characteristics over the range of temperatures expected within the disk drive. Those compounds that have been found or are believed to be useful in the present invention include, but are not limited to, natural rubbers, butyl rubbers, silicone rubbers, polyacrylate rubbers, nitrile rubbers, isoprene rubbers, butadiene rubbers, EPT rubber, polyether rubbers, thermoplastic rubbers, fluorosilicones, fluoroelastomers, polychloroprene, polyacrylate, polyurethanes, acrylonitriles, styrene butadienes, epoxy resins, various other compounds displaying elastomer-like properties, and blends of any of the above. Examples of specific elastomer-like materials which are believed desirable for use according to the principles of the present invention include the elastomer chloroprene manufactured by Bayer under the trade name Baypren; polychloroprene manufactured by Denki USA under the trade name Denka; and neoprene manufactured by DuPont under the trade name Neoprene. Other examples include urethane copolymers of diisocyanate having a polyester or polyether base, such as those manufactured by Uniroyal under the trade names Vibrathane and Adiprene and by TSE Industries under the trade name Millathane. Additional examples include fluoroelastomers or fluorocarbon elastomers, such as those manufactured by 3M Company under the trade names Fluorel and Aflas, by DuPont under the trade name Viton and by Ausimont USA under the trade name Tecnoflon. Further examples include the ethylene/acrylic elastomers manufactured by DuPont under the trade name VAMAC; the acrylic elastomers manufactured by Zeon Chemical under the trade name Hytemp; and the chlorosul fonated polyethylenes manufactured by DuPont under the trade name Hypalon. Of these specific examples of elastomers- like compounds 64, the Viton and Neoprene manufactured by DuPont appear to be the most desirable. The elastomer-like compound of the present invention may be a blend of various compounds containing elastomer-like properties. It is desirable for the elastomer-like compound to have a hardness of from about 5 to about 90 on a Shore A scale, and more desirable to have a hardness of from about 20 to about 80 on a Shore A scale. Of course, one of ordinary skill in the art will recognize that the optimum elastomer-like compound employed and the optimum range of Shore A hardness, as well as other properties, will depend upon the particular application in which the present invention is employed. The elastomer-like compound 64 is molded to the desired components of the disk drive 10, rather than formed as separate and discrete disk drive components, and later assembled to form the disk drive. It is believed that any suitable molding technique well known in the art, such as transfer molding, injection molding or compression molding, can be employed in the present invention. It has been found desirable to employ transfer molding techniques. In general, transfer molding involves using both heat and pressure to soften an elastomer-like compound located in a transfer chamber or cavity, and then forcing the softened material under high pressure through an orifice or transfer port into a closed mold where vulcanization and final curing take place. It is desirable for the elastomer-like compound to be allowed to cure for between about two minutes to about thirty minutes at temperatures ranging between about 250°F to about 400°F (121°C to 204°C) and more desirably at temperatures ranging between about 320°F to about 360°F (160°C to 182°C) . Satisfactory results have been obtained with samples of the stator motor components molded with the DuPont elastomer Neoprene, where the Neoprene has a Shore A hardness of 65, a tensile strength of 2,150 psi, an elongation of 630%, a 200% modulus of 1,175 psi and a specific gravity of 1.57. These mechanical properties were obtained by curing the Neoprene elastomer for fifteen (15) minutes at 324°F (162°C) . Satisfactory results have also been obtained with samples of the stator motor and pivot assembly components molded with the DuPont elastomer Viton, where the Viton has a Shore A hardness of about 71, a tensile strength of about 1,452 psi, and elongation of about 341%, a 100% modulus of about 495 psi and a specific gravity of about 1.84. These properties were obtained by curing the Viton elastomer for eight (8) minutes at 350°F (177°C) . The test results of other elastomer-like compounds believed to suitable for applications in accordance with the present invention tabulated below: It is desirable for the disk drive component surface to be prepared before the molding step so as to improve bonding with the elastomer-like compound. Satisfactory results have been obtained with an exemplary surface preparation which includes first removing oil and other contaminants from the surface being molded to by using a suitable degreasing solvent or aqueous solution. Next, the surface to be molded is roughened or otherwise textured, for example, by sand blasting the surface with aluminum oxide "54" grit using compressed air or by a chemical etching method. After the surface has been textured, a primer is applied to the surface by brushing, spraying, etc.. It is desirable for the primer to be applied at room temperature or between about 65°F to about 90°F (18°C to 32°C) . Once applied, the primer is allowed to dry for at least about thirty (30) minutes to about an hour before the molding process is begun. While it is more desirable for the surface preparation to include both texturing and the use of a primer, the present invention is not intended to be so limited. For some applications, it may be desirable to only employ one or the other (i.e., texturing or the use of a primer). When the DuPont elastomer Viton is used, satisfactory results have been obtained with a primer manufactured by Lord Corporation of Erie, Pennsylvania under the trade name Chemlok Adhesive 5150. When the DuPont elastomer Neoprene is used, satisfactory have been obtained using a primer manufactured by Morton International of West Alexandria, Ohio under the trade name Thixon Adhesive OSN-2. After the molded disk drive component is removed from the mold cavity, it may be desirable to subject the as-molded elastomer-like compound to a post- cure bake in order to optimize its mechanical properties. When the DuPont elastomer Viton is used, a post-cure bake at 400°F (204°C) for sixteen (16) hours has been found to cause an improvement in the mechanical properties of the elastomer. Such a post-cure bake may not be necessary for the DuPont elastomer Neoprene. The method of the present invention, for dampening vibrations in a disk drive, includes the step of providing a disk drive having various components with an elastomer-like compound molded thereto, as described earlier. The inclusion of selective components which have an elastomer-like compound molded thereto significantly reduces vibrations within the disk drive when the disk drive is operated. Of course, one of ordinary skill in the art will recognize that the amount of such a reduction will depend upon the particular design and style of the disk drive being employed, the amount of vibration present in the disk drive when selective components do not have an elastomer-like compound molded thereto, and the thickness and other dimensions of the molded elastomer-like compound. In general, the principles of the present invention can enable a disk drive to experience a reduction in vibrations of as low as about 75 decibels, as low as about 50 decibels, or even lower. Having described the present invention in detail and by reference to the exemplary embodiments described hereinabove, it will be apparent to a person of skill in the art that numerous modifications and variations to the exemplary embodiments are possible without departing from the scope of the present invention as defined in the appended claims. What is claimed is:

Claims: 1. A disk drive assembly comprising an enclosure housing a plurality of disk drive components including at least one head for at least one of recording and reading information on at least one disk-like recording medium, an actuator assembly supporting said head, a pivot assembly rotatably supporting said actuator assembly and a motor for rotating said recording medium, at least one of said motor and said pivot assembly including at least one elastomer-like compound molded to a portion thereof by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 2. The disk drive assembly as set forth in claim 1, wherein said pivot assembly includes a pivot shaft having an outer diameter, and said at least one elastomer-like compound is molded to the outer diameter of said pivot shaft by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 3. The disk drive assembly as set forth in claim 1, wherein said pivot assembly includes a pivot shaft and at least one pivot bearing disposed between said pivot shaft and said actuator assembly, said at least one pivot bearing has an inner diameter and an outer diameter, and said at least one elastomer-like compound is molded to at least one of the inner diameter and the outer diameter of said at least one pivot bearing by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 4. The disk drive assembly as set forth in claim 1, wherein said pivot assembly includes at least one pivot bearing and a pivot housing disposed between said at least one pivot bearing and said actuator assembly, said pivot housing has an inner diameter, and said at least one elastomer-like compound is molded to the inner diameter of said pivot housing by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 5. The disk drive assembly as set. forth in claim 1, wherein said pivot assembly includes a pivot shaft, a pivot housing and at least one pivot bearing, and said at least one elastomer-like compound is molded to a surface on at least one of said pivot shaft, said pivot housing and said at least one pivot bearing by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 6. The disk drive assembly as set forth in claim 1, wherein said motor includes a motor shaft supporting the rotation of said at least one recording medium and said at least one elastomer-like compound is molded to at least one portion of said motor shaft by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 7. The disk drive assembly as set forth in claim 6, wherein said motor includes a motor hub mounted on said motor shaft and a motor stator operatively adapted to cooperate with said motor hub to rotate said at least one recording medium, and said at least one elastomer- like compound is molded to said motor shaft so as to be disposed between said motor shaft and said motor hub by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 8. The disk drive assembly as set forth in claim 6, wherein said at least one elastomer-like compound is molded into at least two molded sections disposed axially apart on said motor shaft by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 9. The disk drive assembly as set forth in claim 6, wherein said at least one elastomer-like compound is molded into a molded body section of generally uniform thickness on said motor shaft by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 10. The disk drive assembly as set forth in claim 6, wherein said at least one elastomer-like compound is molded into two molded sections disposed axially apart on said motor shaft and in a molded body section of generally uniform thickness on said motor shaft by a molding process so as to improve vibration dampening characteristics in said disk drive assembly, said molded body section being thinner than and disposed between said molded sections. 11. The disk drive assembly as set forth in claim 1, wherein said motor includes a motor shaft supporting the rotation of said at least one recording medium and at least one spindle bearing disposed between said motor shaft and said at least one recording medium, said at least one spindle bearing has an inner diameter and an outer diameter, and said at least one elastomer-like compound is molded to at least one of the inner diameter and the outer diameter of said at least one spindle bearing by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 12. The disk drive assembly as set forth in claim 1, wherein said motor includes a motor stator operatively adapted to rotate said at least one recording medium, said motor stator has an upper surface, a lower surface, an interior diameter surface, and an outer diameter surface, and said at least one elastomer-like compound is molded to at least one of the upper surface, lower surface, interior diameter surface and outer diameter surface of said motor stator by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 13. The disk drive assembly as set forth in claim 1, wherein said motor includes a stator having an interior diameter, an outer diameter and a series of stator poles, said stator poles are disposed along said interior diameter and said at least one elastomer-like compound is molded to said outer diameter by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 14. The disk drive assembly as set forth in claim 1, wherein said motor includes a stator having an interior diameter, an outer diameter and a series of stator poles, said stator poles are disposed along said outer diameter and said at least one elastomer-like compound is molded to said interior diameter by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 15. The disk drive assembly as set forth in claim 1, wherein said motor includes a motor shaft supporting the rotation of said at least one recording medium, at least one spindle bearing disposed between said motor shaft and said at least one recording medium, a motor hub mounted on said motor shaft and a motor stator operatively adapted to cooperate with said motor hub to rotate said at least one recording medium, and said at least one elastomer-like compound is molded to a surface of at least one of said motor shaft, said spindle bearing and said motor stator by a molding process so as to improve vibration dampening characteristics in said disk drive assembly. 16. The disk drive assembly as set forth in at least one of claims 1 - 15, wherein said at least one elastomer-like compound is molded to at least one of a primed surface and a textured surface of a portion of at least one of said motor and said pivot assembly. 17. The disk drive assembly as set forth in at least one of claims 1 - 16 wherein said at least one elastomer-like compound is at least one of chemically bonded to and mechanically bonded to the portion it is molded to. 18. A method for improving vibration dampening characteristics in disk drives, said method comprising the steps of: providing a disk drive assembly having a plurality of disk drive components including at least one head for at least one of recording and reading information on at least one disk-like recording medium, an actuator assembly supporting the head, a pivot assembly rotatably supporting the actuator assembly and a motor for rotating the recording medium, at least one of the motor and the pivot assembly including at least one elastomer¬ like compound; selecting the elastomer-like compound so as to be suitable for dampening undesirable vibrations within the disk drive assembly; molding the elastomer-like compound to a portion of at least one of the motor and the pivot assembly; and assembling at least one of the motor and the pivot assembly into the disk drive assembly, after the molding of the elastomer-like compound to the portion thereof. 19. The method as set forth in claim 18, wherein before said molding step, said method includes the step of removing contaminates from a surface of the portion having the elastomeric-like compound molded thereto. 20. The method as set forth in at least one of claims 18 and 19, wherein before said molding step, said method includes the step of at least one of texturing and applying a primer to a surface of the portion having the elastomeric-like compound molded thereto. 21. The method as set forth in at least one of claims 18 - 20, wherein said molding step includes at least one of chemically bonding and mechanically bonding the elastomeric-like compound to a surface of the portion. 22. The method as set forth in at least one of claims 18 - 21, wherein said molding step includes at least one of transfer molding, injection molding, compression molding and like molding of the elastomer¬ like compound to a portion of at least one of the motor and the pivot assembly. 23. The method as set forth in at least one of claims 18 - 22, wherein after said molding step, the elastomer-like compound molded to the portion is baked to improve its properties.

Inventors: BACK FOREST HIRAM, BACK JAMES WILLIAM, BACK, FOREST, HIRAM, BACK, JAMES, WILLIAM
Applicants: RUBBER TECH INC, RUBBER-TECH, INC.
Application year: 1996
Main classification: G11B33
IPC codes: G11B19, G11B25, G11B33, H02K1, H02K5