United States Patent [19]
`United States Patent [191
`Dunfield et aI.
`Dun?eld et a].
`
`11111 m 11111111111111111111111111111111111111
`USOO5694268A
`US005694268A
`[11] Patent Number:
`[11] Patent Number:
`[45] Date of Patent:
`[45] Date of Patent:
`
`5,694,268
`5,694,268
`Dec. 2, 1997
`Dec. 2, 1997
`
`[54] SPINDLE MOTOR HAVING OVERMOLDED
`[54] SPINDLE MOTOR HAVING OVERMOLDED
`STATOR
`STATOR
`
`[75]
`Inventors: John Charles Dunfield. Santa Cruz;
`
`
`[75] Inventors: John Charles Dun?eld. Santa Cruz; 591” Km Hem'Apms‘ b°th °f .
`Gunter Karl Heine. Aptos, both of
`Calif.
`'
`
`.
`[73] Assignee: Seagate Technology, Inc •• Scotts
`[73] AS5191“: Seagate TeFhmhgY! Inc" Soot“
`Valley, Calif.
`Valley, Ca11f~
`
`[211 App]. No_; 550,175
`[21] Appl. No.: 550,175
`
`[22] Filed:
`22 Filed:
`[
`]
`
`Oct. 30, 1995
`Oct. 30, 1995
`
`Related U.S. AppHcatiOD Data
`Related {15- Al’l'?m?m Data
`
`[63] Continuation-impart of Ser. No. 386,883, Feb. 10, 1995.
`[63]
`continuation-ill-part of Ser. No. 386,883, Feb. 10, 1995.
`lot. CL 6
`6
`.
`.
`[51]
`............................. GlIB 17102; H02K 5/24;
`[51] Int. Cl. ........................... .. GllB 17/02,
`H02K 7/14
`[52] U.S. CI ...................................... 3CJO/98.07; 360/99.08;
`[52] US. Cl. ...........................
`310/67 R; 310151; 310/254
`[58] Field of Search .............................. 360/97.01, 98.01.
`[58] Field of Search ............................ .. 360/9701. 98.01.
`360198.07, 98.08. 99.04. 99.08-99.12; 310/51.
`360/98.07,98.08,99.04,99.08-99.12; 310/51,
`67 R. 254
`67 R. 254
`
`[56]
`[56]
`
`References Cited
`RefeftDces Cited
`,TENT Cm ‘EMT
`U.S. PATENT DOCUMENTS
`US' P
`DO
`S
`1,688,891 10/1928 Spreen .................................... .. 310/51
`1,688,891 10/1928 Spreen ...................................... 310/51
`4/1969 Frohmuller et aI ....................... 310/51
`3,438,407
`3,438,407
`4/1969 Frohmuller et a1.
`310/51
`3,546,504 12/1970 Janssen et aI ............................. 310/51
`3,546,504 12/1970 Jan-88911.6! 31
`310/51
`5/1981 Fernstrom ............................... 4181270
`4,268,233
`4268233 5/1981 Fems'mm
`418/270
`3/1987 von der Heide et aI. ................ 310/51
`4,647,803
`goggle’ Heme ct 31'
`611987 Seitz .......................................... 310/90
`4,672,250
`‘760,299 7/l988 De;
`"""""" "
`310/91
`7/1988 Dickie et aI .............................. 310191
`4,760,299
`4'816 710 3/1939 S?vaggio ex'
`:"3101194
`3/1989 Silvaggio et aI ....................... 3101194
`4,816,710
`4,823,034
`4/1989 Wrobel .................................. 310/67 R
`4,823,034
`4/1989 Wrobel .............. ..
`310/67R
`4,965,476 10/1990 Lin ............................................ 310/51
`4,965,476 1011990 Lin .......................................... .. 310/51
`
`. . . . .. 310/905
`
`5,126,612
`
`6/1992 Girault . . . . .
`
`1/1992 Jones ......................................... 310191
`5,079,466
`1/1992 Jones ....................................... .. 310/91
`5,079,466
`3/1992 Ueki et aI .............................. 360197.2
`5,097,366
`3/1992 Ueki et a1.
`.. 360/972
`5,097,366
`611992 Girault ................................... 310/90.5
`5,126,612
`411993 Fruge
`5,200,866
`.................................. 360199.08
`7/1993 Ogawa ...................................... 310/90
`
`
`
`gmgé ‘71; 11/1993 Fazekas gawa .
`310/51
`
`, 5,235,227
`5,227,686
`811993 Fazekas ..................................... 310/51
`5,235,227
`811993 Katakura et aI .......................... 310/51
`5,241,229
`8/1993 Katakura et
`5,241,229
`310/51
`1011994 MacLeod ............................. 360198.07
`5,352,947
`5,352,947 1011994 MacLeod ..
`360/9807
`.
`5,367,418 11/1994 Chessman et 21.
`360/9912
`11/1994 Chessman et aI ................... 360199.12
`5,367,418
`1211994 Elsing et aI ............................... 310/67
`5,376,850
`5,376,850 12/1994 Elsing et a1.
`...... .. 310/67
`1011995 Hattori et aI.
`.. ..................... 360199.08
`5,457,588 10/1995 Hattori et a1.
`360/9908
`5,457,588
`5/1996 Yamada et aI ....................... 360198.07
`5519170 5/1996 Yam/1111161111.
`360/9807
`5,519,270
`1111996 Dunfield et aI ...................... 360199.08
`5,579,188
`5,579,188 11/1996 Dun?eld et a1. .... ..
`360199.08
`
`FOREIGN PATENT DOCUMENTS
`FOREIGN PATENT DOCUMENTS
`
`7701273 10/1967 Canada .................................. .. 310/70
`770273 1011967 Canada .................................... 31OnO
`3-89838 (A)
`Japan.
`411991
`3-89838 A 4/1991 .1
`.
`4463;42)
`apan
`4-168942
`611992
`Japan.
`(AA)
`(AA) 6/1992 Japan .
`4451542 (A)
`9/1992 Japan I
`4-251542 (A)
`Japan.
`9/1992
`4364340 (A) 1W199Q Japan.
`4-364340 (A) 1211992
`Japan.
`2 154 on 3/1935 United Kingdom .
`8/1985 United Kingdom.
`2 154 072
`
`Primary Examiner-Jefferson Evans
`_
`Primary EWWMPJCFMSO" Evans
`Attome)\ Agent, or Finn-Westman, Champlin & Kelly,
`Mame» Agent’ 0' F"m—w'=S‘m"~ ChamPhn & Kelly»
`P.A.
`BA
`
`ABSTRACT
`[57]
`ABSTRACT
`[57]
`A disc drive spindle motor for rotating at least one disc in a
`A disc drive spindle motor for rotating at least one disc in a
`data storage device includes a base. a shaft. a rotor and a
`data storage device includes a base, a shaft, a rotor and a
`stator. A bearing interconnects the rotor with the shaft and
`stator. A bearing interconnects the rotor with the shaft and
`allows the rotor to rotate about the shaft. An overrnold
`allows the rotor to rotate about the shaft. An overmold
`encapsulates at least a portion of the stator and provides the
`encapsulates at least a portion of the stator and provides the
`stator with a smooth external surface. The overmold
`stator with a smooth external surface. The overmold
`mechanically isolates the stator from the base and damps
`mechanically isolates the stator from the base and damps
`sympathetic vibrations in the stator structure to reduce the
`sympathetic vibrations in the stator structure to reduce the
`generation of acoustic noise in the storage device.
`generation of acoustic noise in the storage device.
`
`31 Claims, 14 Drawing Sheets
`31 Claims, 14 Drawing Sheets
`
`426---·
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`
`434
`
`Page 1 of 22
`
`PETITIONERS' EXHIBIT 1013
`
`

`

`u.s. Patent
`US. Patent
`
`Dec. 2, 1997
`Dec. 2, 1997
`
`Sheet 1 of 14
`Sheet 1 of 14
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`5,694,268
`5,694,268
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`Page 2 of 22
`
`

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`u.s. Patent
`US. Patent
`
`Dec. 2, 1997
`Dec. 2, 1997
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`

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`US. Patent
`
`Dec. 2, 1997
`Dec. 2, 1997
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`Dec. 2, 1997
`Dec. 2, 1997
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`U.S. Patent
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`Dec. 2, 1997
`Dec. 2, 1997
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`US. Patent
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`Dec. 2, 1997
`Dec. 2, 1997
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`Sheet 9 0f 14
`Sheet 9 of 14
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`US. Patent
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`Dec. 2, 1997
`Dec. 2, 1997
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`Sheet 10 of 14
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`

`u.s. Patent
`US. Patent
`
`Dec. 2, 1997
`Dec. 2, 1997
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`Sheet 12 of 14
`Sheet 12 of 14
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`u.s. Patent
`US. Patent
`
`Dec. 2, 1997
`Dec. 2, 1997
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`Sheet 13 of 14
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`u.s. Patent
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`US. Patent
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`Dec. 2, 1997
`Dec. 2, 1997
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`Sheet 14 of 14
`Sheet 14 of 14
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`5,694,268
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`2
`2
`at a constant speed. Typical spindle motor speeds have been
`at a constant speed. lYPica1 spindle motor speeds have been
`in the range of 3600 RPM. Current technology has increased
`in the range of 3600 RPM. Current technology has increased
`spindle motor speeds to 4800 RPM. 7200 RPM and above.
`spindle motor speeds to 4800 RPM. 7200 RPM and above.
`Analysis of various types of disc drives has brought to light
`Analysis of various types of disc drives has brought to light
`5 several different modes of acoustic noise generation which
`several di?erent modes of acoustic noise generation which
`are attributable to the spindle motor and its control logic.
`are attributable to the spindle motor and its control logic.
`One mode of noise generation is sympathetic vibration of
`One mode of noise generation is sympathetic vibration of
`the disc drive housing in response to the rotating mass of the
`the disc drive housing in response to the rotating mass of the
`spindle motor. Another mode of acoustic noise generation is
`spindle motor. Another mode of acoustic noise generation is
`electromagnetic disturbances caused by the excitation of the
`10 electromagnetic disturbances caused by the excitation of the
`10
`stator mass by the application and removal of the commu(cid:173)
`stator mass by the application and removal of the commu
`tation pulses that are used to drive the motor and control its
`tation pulses that are used to drive the motor and control its
`speed. The commutation pulses are timed. polarization
`speed. The commutation pulses are timed, polarization(cid:173)
`selected DC current pulses which are directed to sequen-
`selected DC current pulses which are directed to sequen
`tially selected stator windings. The rapid rise and fall times
`15 tially selected stator windings. The rapid rise and fall times
`15
`of these pulses act as a striking force and set up sympathetic
`of these pulses act as a striking force and set up sympathetic
`vibrations in the stator structure.
`vibrations in the stator structure.
`If the stator structure is rigidly connected to the disc drive
`If the stator structure is rigidly connected to the disc drive
`housing. either directly or through a rigid material. these
`housing, either directly or through a rigid material, these
`20
`20 vibrations are coupled to the housing and generate resonant
`vibrations are coupled to the housing and generate resonant
`vibrations in the housing causing unacceptable levels of
`vibrations in the housing causing unacceptable levels of
`acoustic noise.
`acoustic noise.
`Prior art attempts to reduce or eliminate noise include
`Prior art attempts to reduce or eliminate noise include
`controlling the resonant frequency of the housing. and
`controlling the resonant frequency of the housing, and
`damping the vibration of the housing. In US. Pat. No.
`damping the vibration of the housing. In U.S. Pat. No.
`5.376.850. acoustic noise is reduced by uncoupling the
`5,376,850, acoustic noise is reduced by uncoupling the
`stator from hard contact with the stationary portion of the
`stator from hard contact with the stationary portion of the
`shaft. A plurality of O-rings interposed radially between the
`shaft. A plurality of O-rings interposed radially between the
`stator and the shaft of the spindle motor. Also, a non-metallic
`stator and the shaft of the spindle motor. Also. a non-metallic
`washer is positioned at one end of the shaft and an axial
`washer is positioned at one end of the shaft and an axial
`O-ring is positioned at the other end of the shaft.
`O-ring is positioned at the other end of the shaft.
`
`25
`25
`
`30
`
`1
`1
`SPINDLE MOTOR HAVING OVERMOLDED
`SPINDLE MOTOR HAVING OVERMOLDED
`STATOR
`STATOR
`CROSS-REFERENCE TO RELATED
`CROSS-REFERENCE TO RELATED
`APPLICATION
`APPUCATION
`This application is a continuation-in-part of U.S. Ser. No.
`This application is a continuation-in-part of US. Ser. No.
`081386,883, filed Feb. 10, 1995.
`08/386383. ?led Feb. 10. 1995.
`BACKGROUND OF THE INVENTION
`BACKGROUND OF THE INVENTION
`The present invention relates generally to the field of disc
`The present invention relates generally to the ?eld of disc
`drive spindle motors for data storage devices and, more
`drive spindle motors for data storage devices and. more
`particularly, to a spindle motor in which the stator has a
`particularly. to a spindle motor in which the stator has a
`resilient overmold to isolate the stator from a base of the
`resilient overmold to isolate the stator from a base of the
`storage device.
`storage device.
`Disc drive data storage devices, known as "Winchester"
`Disc drive data storage devices. known as “Winchester”
`type disc drives, are well-known in the industry. In a
`type disc drives. are well-known in the industry. In a
`Winchester disc drive, digital data are written to and read
`Winchester disc drive. digital data are written to and read
`from a thin layer of magnetizable material on the surface of
`from a thin layer of magnetizable material on the surface of
`rotating discs. Write and read operations are performed
`rotating discs. Write and read operations are performed
`through a transducer which is carried in a slider body. The
`through a transducer which is carried in a slider body. The
`slider and transducer are sometimes collectively referred to
`slider and transducer are sometimes collectively referred to
`as a head. and typically a single head is associated with each
`as a head. and typically a single head is associated with each
`disc surface. The heads are selectively moved under the
`disc surface. The heads are selectively moved under the
`control of electronic circuitry to anyone of a plurality of
`control of electronic circuitry to any one of a plurality of
`circular, concentric data tracks on the disc surface by an
`circular. concentric data tracks on the disc surface by an
`actuator device. Each slider body includes a self-acting
`actuator device. Each slider body includes a self-acting
`hydrodynamic air bearing surface. As the disc rotates. the
`hydrodynamic air bearing surface. As the disc rotates. the
`disc drags air beneath the air bearing surface. which devel
`disc drags air beneath the air bearing surface, which devel(cid:173)
`ops a lifting force that causes the slider to lift and fly several
`ops a lifting force that causes the slider to lift and ?y sevm'al
`microinches above the disc surface.
`microinches above the disc surface.
`In the current generation of disc drive products, the most
`In the current generation of disc drive products. the most
`commonly used type of actuator is a rotary moving coil
`commonly used type of actuator is a rotary moving coil
`actuator. The discs themselves are typically mounted in a
`actuator. The discs themselves are typically mounted in a
`"stack" on the hub structure of a brushless DC spindle
`“stack” on the hub structure of a brushless DC spindle
`motor. The rotational speed of the spindle motor is precisely
`motor. The rotational speed of the spindle motor is precisely
`controlled by motor drive circuitry which controls both the
`controlled by motor drive circuitry which controls both the
`timing and the power of commutation signals directed to the
`timing and the power of commutation signals directed to the
`stator windings of the motor.
`stator windings of the motor.
`The first Winchester disc drives to be produced were large
`The ?rst Winchester disc drives to be produced were large
`cabinet models which included discs having a diameter of 14
`cabinet models which included discs having a diameter of 14
`inches and AC induction spindle motors. These types of disc
`inches and AC induction spindle motors. These types of disc
`drives were commonly located in dedicated "computer
`drives were commonly located in dedicated “computer
`rooms" with large mainframe computers, where environ(cid:173)
`rooms” with large mainframe computers. where environ
`mental factors such as temperature and humidity could be
`mental factors such as temperature and humidity could be
`carefully controlled. In this type of environment, the acous(cid:173)
`carefully controlled. In this type of environment, the acous
`tic noise generated by cooling fans and disc drive motors
`tic noise generated by cooling fans and disc drive motors
`was of little concern. since the only persons directly in
`was of little concern. since the only persons directly in
`contact with the systems were maintenance personnel. who
`contact with the systems were maintenance personnel. who
`were generally not in the computer rooms for extended
`were generally not in the computer rooms for extended
`periods of time. The users of such systems were typically
`periods of time. The users of such systems were typically
`located at a remote location and communicated with the
`located at a remote location and communicated with the
`computer system via keyboards and display terminals which
`computer system via keyboards and display terminals which
`did not generate excessive amounts of acoustic noise.
`did not generate excessive amounts of acoustic noise.
`More recently, personal computers have become more
`More recently, personal computers have become more
`popular and are commonly located within the work space of
`popular and are commonly located within the work space of
`the system user. This has prompted an increase in awareness
`the system user. This has prompted an increase in awareness
`of acoustic noise generated by the disc drives located within
`of acoustic noise generated by the disc drives located within
`the personal computers. In certain markets. such as Europe,
`the personal computers. In certain markets. such as Europe.
`the amount of acoustic noise allowable in the work place is
`the amount of acoustic noise allowable in the work place is
`closely regulated. With this in mind. it has become common
`closely regulated. With this in mind. it has become common
`for system manufacturers to impose a "noise budget" on
`for system manufacturers to impose a “noise budget” on
`manufacturers of major system components, such as disc
`manufacturers of major system components. such as disc
`drives, which limits the amount of acoustic noise that such
`drives. which limits the amount of acoustic noise that such
`components can contribute to the overall noise of the
`components can contribute to the overall noise of the
`system.
`system.
`One of the principal sources of noise in disc drive data
`One of the principal sources of noise in disc drive data
`storage devices is the spindle motor which drives the discs
`storage devices is the spindle motor which drives the discs
`
`45
`45
`
`35
`35
`
`SUMMARY OF THE INVENTION
`SUMMARY OF THE INVENTION
`The present invention is a disc drive spindle motor for
`The present invention is a disc drive spindle motor for
`rotating at least one disc in a data storage device. The motor
`rotating at least one disc in a data storage device. The motor
`includes a base, a stationary member, a rotor and a stator. A
`includes a base. a stationary member. a rotor and a stator. A
`bearing interconnects the rotor with the stationary member
`bearing interconnects the rotor with the stationary member
`and allows the rotor to rotate about the stationary member.
`and allows the rotor to rotate about the stationary member.
`40 An overmold encapsulates at least part of the stator and
`An overmold encapsulates at least part of the stator and
`provides the stator with a smooth external surface. The
`provides the stator with a smooth external surface. The
`overmold mechanically isolates the stator from the base and
`overmold mechanically isolates the stator from the base and
`damps sympathetic vibrations in the stator structure to
`darnps sympathetic vibrations in the stator structure to
`reduce the generation of acoustic noise in the storage device.
`reduce the generation of acoustic noise in the storage device.
`The overmold provides a convenient structure for mount-
`The overmold provides a convenient structure for mount
`ing the stator to the base. In one embodiment, the stator
`ing the stator to the base. In one embodiment. the stator
`includes a plurality of phase windings which are disposed
`includes a plurality of phase windings which are disposed
`about the stator and spaced apart by gaps. The overmold ?lls
`about the stator and spaced apart by gaps. The overmold fills
`the gaps and substantially encapsulates the stator. A plurality
`the gaps and substantially encapsulates the stator. A plurality
`50 of mounting apertures extend in an axial direction through
`of mounting apertures extend in an axial direction through
`the overmold in the gaps between the phase windings. A
`the overmold in the gaps between the phase windings. A
`mounu'ng pin extends through each mounting aperture and
`mounting pin extends through each mounting aperture and
`has a distal end which can be attached to the base by
`has a distal end which can be attached to the base by
`heat-staking. for example.
`heat-staking, for example.
`In another embodiment, the overmold comprises at a
`In another embodiment. the overmold comprises at a
`plurality of mounting ears extending from a circumference
`plurality of mounting ears extending from a circumference
`of the stator in a radial direction for connection to the base.
`of the stator in a radial direction for connection to the base.
`The mounting ears can include a rigid material, such as
`The mounting ears can include a rigid material. such as
`plastic or metal, which is encapsulated by the overmold or
`plastic or metal. which is encapsulated by the overmold or
`60 exposed to provide a rigid yet isolated connection.
`exposed to provide a rigid yet isolated connection.
`In another embodiment, the overmold has a circumferen(cid:173)
`In another embodiment. the overmold has a circumferen
`tial side wall opposite to the rotor having an annular raised
`tial side wall opposite to the rotor having an annular raised
`projection. The projection is compressed between the stator
`projection. The projection is compressed between the stator
`and the base to secure the stator within the base. In yet
`and the base to secure the stator within the base. In yet
`65 another embodiment, the stator is adhered to the base
`another embodiment. the stator is adhered to the base
`65
`through a polyester plastic ?lm having ?rst and second
`through a polyester plastic film having first and second
`surfaces which carry a pressure sensitive adhesive.
`surfaces which carry a pressure sensitive adhesive.
`
`55
`55
`
`Page 16 of 22
`
`

`

`5,694,268
`5,694,268
`
`4
`4
`FIG. 21 is a sectional view of an overmolded stator in
`FIG. 21 is a sectional view of an overrnolded stator in
`which the overmold is limited to an outer diameter of the
`which the overmold is limited to an outer diameter of the
`stator.
`stator.
`AG. 22 is a fragmentary sectional view of a spindle motor
`FIG. 22 is a fragmentary sectional view of a spindle motor
`having an overmolded stator with a radial position that is
`having an overrnolded stator with a radial position that is
`internal to the rotor.
`internal to the rotor.
`
`3
`3
`While the present invention is useful in disc drive spindle
`While the present invention is useful in disc drive spindle
`motors having ball bearings, the present invention is par(cid:173)
`motors having ball bearings. the present invention is par
`ticularly useful in hydrodynamic bearing motors to reduce or
`ticularly useful in hydrodynamic bearing motors to reduce or
`eliminate pure vibration tones which become more notice(cid:173)
`eliminate pure vibration tones which become more notice
`able with lower levels of background vibration. The over-
`able with lower levels of background vibration. The over
`molded stator can have an axial position which is within or
`rnolded stator can have an axial position which is within or
`below the hub, and can have a radial position which is
`below the hub. and can have a radial position which is
`internal or external to the rotor. The overmold provides the
`internal or external to the rotor. The overmold provides the
`stator with an environmental seal having a smooth external
`stator with an environmental seal having a smooth external
`surface which is substantially free of apertures. The over- 10
`surface which is substantially free of apertures. The over
`10
`mold can be cleaned more easily during production than a
`mold can be cleaned more easily during production than a
`bare stator and therefore reduces impurities in the disc drive.
`bare stator and therefore reduces impurities in the disc drive.
`The overmold provides a large surface area over which
`The overmold provides a large surface area over which
`vibrations can be damped to reduce acoustic noise genera(cid:173)
`vibrations can be damped to reduce acoustic noise genera
`tion. The overmold also allows a greater integration of parts 15
`tion. The overmold also allows a greater integration of parts
`which reduces the number of parts that must be assembled
`which reduces the number of parts that must be assembled
`in the disc drive.
`in the disc drive.
`
`5
`
`DETAILED DESCRIPTION OF THE
`DErAILED DESCRlPITON OF THE
`PREFERRED EMBODIMENTS
`PREFERRED EMBODIMENfS
`The present invention is a spindle motor for a disc drive
`The present invention is a spindle motor for a disc drive
`data storage device in which the stator is isolated from the
`data storage device in which the stator is isolated from the
`base to reduce acoustic levels in the storage device. FIG. 1
`base to reduce acoustic levels in the storage device. FIG. 1
`is a plan view of a typical disc drive 10 in which the present
`is a plan view of a typical disc drive 10 in which the present
`invention is useful. Disc drive 10 includes a housing base 12
`invention is useful. Disc drive 10 includes a housing base 12
`and a top cover 14. The housing base 12 is combined with
`and a top cover 14. The housing base 12 is combined with
`top cover 14 to form a sealed environment to protect the
`top cover 14 to form a sealed environment to protect the
`internal components from contamination by elements from
`internal components from contamination by elements from
`outside the sealed environment.
`outside the sealed environment.
`The base and top cover arrangement shown in FIG. 1 is
`The base and top cover arrangement shown in FIG. 1 is
`common in the industry. However. other arrangements of the
`common in the industry. However, other arrangements of the
`housing components have been frequently used. and the
`housing components have been frequently used. and the
`present invention is not limited to the con?guration of the
`present invention is not limited to the configuration of the
`disc drive housing. For example. disc drives have been
`disc drive housing. For example, disc drives have been
`manufactured using a vertical split between two housing
`25 manufactured using a vertical split between two housing
`25
`members. In such drives. that portion of the housing half
`members. In such drives, that portion of the housing half
`which connects to the lower end of the spindle motor is
`which connects to the lower end of the spindle motor is
`analogous to base 12. while the opposite side of the same
`analogous to base 12, while the opposite side of the same
`housing member. which is connected to or adjacent the top
`housing member, which is connected to or adjacent the top
`of the spindle motor. is functionally the same as the top
`30 of the spindle motor, is functionally the same as the top
`cover 14.
`cover 14.
`Disc drive 10 further includes a disc pack 16 which is
`Disc drive 10 further includes a disc pack 16 which is
`mounted for rotation on a spindle motor (not shown) by a
`mounted for rotation on a spindle motor (not shown) by a
`disc clamp 18. Disc pack 16 includes a plurality of indi
`disc clamp 18. Disc pack 16 includes a plurality of indi(cid:173)
`vidual discs which are mounted for co-rotation about a
`vidual discs which are mounted for co-rotation about a
`central axis. Each disc surface has an associated head 20
`central axis. Each disc surface has an associated head 20
`which is mounted to disc drive 10 for communicating with
`which is mounted to disc drive 10 for communicating with
`the disc surface. In the example shown in AG. 1, heads 20
`the disc surface. In the example shown in FIG. 1. heads 20
`are supported by flexures 22 which are in turn attached to
`are supported by ?exures 22 which are in turn attached to
`40 head mounting arms 24 of an actuator body 26. The actuator
`head mounting arms 24 of an actuator body 26. The actuator
`shown in FIG. 1 is of the type known as a rotary moving coil
`shown in FIG. 1 is of the type known as a rotary moving coil
`actuator and includes a voice coil motor (VCM), shown
`actuator and includes a voice coil motor (V