GB2166586A

GB2166586A - Grounding arrangement for head disk assembly

Info

Publication number: GB2166586A
Application number: GB08526476A
Authority: GB
Inventors: Richard Pearson Casmey
Original assignee: Priam Corp
Current assignee: Priam Corp
Priority date: 1984-10-29
Filing date: 1985-10-28
Publication date: 1986-05-08
Also published as: JPS61160876A; GB8526476D0; DE3538480A1

Abstract

In a head disk assembly, (HDA) a disk clamp 28 is formed with an extended portion which protrudes through the HDA housing. A grounding element including strap 32 is connected between the housing outer surface and the extended clamp portion to form a continuous conductive path between the housing and the disks, thereby dissipating spurious static charge. <IMAGE>

Description

SPECIFICATION Grounding arrangement for head disk assembly This invention relates to a head disk assembly (HDA) and in particular to a means for grounding the static charge generated by rotating disks in the HDA.

An object of this invention is to provide an improved HDA wherein static charge problems are minimized.

In prior known HDA's used in disk drive systems, a centrally located spindle was attached to a drive motor that was located externally to the HDA, thereby enabling rotation of one or more magnetic disks that were mechanically coupled to the spindle. As the disk drive technology progressed and the requirements were for more compact assemblies, the external motor was replaced by an internally located motor assembly employing a stator adjacent to the spindle, and an associated rotor for rotating a hub to which the disks are mounted. In such assemblies, the spindle remains stationary, while the rotor, hub and disks are rotated.

A well known problem associated with disk drives is the loss of data or data error caused by static charge generated by the rotating magnetic disks within the HDA enclosure. Previous attempts to rectify the problem included the provision of grounding elements passed through a bore formed in the spindle to make a connection with the baseplate of the HDA.

The use of a hollow shaft or a spindle weakens the structure, requires more labor and expense to manufacture, and contributes to unwanted stresses and resonances which lead to instability and additional data errors.

In accordance with this invention, a HDA employs a stationary spindle, and a rotating hub to which the magnetic disks are mounted.

A disk clamp is provided which has an extending portion that protrudes from the HDA housing. A conductive ground strap is coupled between the disk clamp extending portion and the housing exterior thus providing a conductive path between the rotating disks and the grounded housing, so that static charge is ef fectiveiy dissipated.

The invention will be described in greater detail with reference to the drawing in which the sole figure is a schematic elevation plan view of a HDA, depicting the inventive assembly.

With reference to the drawing, a HDA incorporates a solid spindle 10, made of stainless steel for example. The spindle has a central cylindrical section 10A and a lower configured section 10B which is seated on a base casting or housing 12. Surrounding the central spindle section 10A, a stator 14 is positioned, which coacts with a rotor 16 closely coupled to the stator. The rotor 16 is formed from permanent magnet material. As is well known, when electric current is supplied to the windings of the stator, the magnetic field of the rotor interacts with the flux generated by the stator windings causing the rotor to rotate.

A hub structure 18, which is attached to the rotor and rotates therewith, supports one or more disks 20, so that when the rotor rotates, the hub and disks rotate accordingly.

The hub structure rotates against support bearings 22 and 24. A fluidic seal 26 is located between the hub and the spindle to prevent the flow of any loose particles between the spindle area and the disk area,thus preventing damage to the disk surfaces which would result in data error. Also, since there is no airflow across bearing 24, the life of the bearing and its lubricant is extended.

A cylindrical disk clamp 28 is seated on the hub structure and against the disks 20 to provide clamping pressure, so that there is no play or give that would allow undue vibration and flutter of the disks. This clamp has an extended cylindrical portion 29 of relatively small diameter which partially protrudes through an aperture 30 formed in the housing 12. To seal the HDA from the external environment, a fluidic seal 31 is provided.

In accordance with this invention, a ground strap 32, which may be a resilient leaf spring made from beryllium copper or bronze, by way of example, is connected at one end to the outer surface of the housing. At the other end of the leaf spring, a connection is made to a conductive grounding button 34, which may be formed from silver graphite, for example. The button 34, which is fixed to the leaf spring, rests on the closed end or base of the cylindrical portion 29 of the disk clamp.

The conductive leaf spring thereby establishes a conductive path between the grounded housing and the rotating disks, via the conductive disk clamp and rotary hub on which the disks are mounted. In this way, any static charge, which may be generated at the disk surfaces by virtue of disk rotation, is bled off and dissipated.

For the purpose of simplicity and convenience, the magnetic head means and actuator for accessing the disk surfaces for recording and readout, which are conventionally provided, are not illustrated.

In contrast to prior art HDA's, wherein grounding leads are disposed within the HDA housing or enclosure and brought through the bore of a hollow spindle, the configuration disclosed herein provides a simple, inexpensive grounding means and a structurally improved HDA.

1. A head disk assembly comprising: at least one magnetic disk a rotary hub to which said disk is mounted;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Grounding arrangement for head disk assembly This invention relates to a head disk assembly (HDA) and in particular to a means for grounding the static charge generated by rotating disks in the HDA. An object of this invention is to provide an improved HDA wherein static charge problems are minimized. In prior known HDA's used in disk drive systems, a centrally located spindle was attached to a drive motor that was located externally to the HDA, thereby enabling rotation of one or more magnetic disks that were mechanically coupled to the spindle. As the disk drive technology progressed and the requirements were for more compact assemblies, the external motor was replaced by an internally located motor assembly employing a stator adjacent to the spindle, and an associated rotor for rotating a hub to which the disks are mounted. In such assemblies, the spindle remains stationary, while the rotor, hub and disks are rotated. A well known problem associated with disk drives is the loss of data or data error caused by static charge generated by the rotating magnetic disks within the HDA enclosure. Previous attempts to rectify the problem included the provision of grounding elements passed through a bore formed in the spindle to make a connection with the baseplate of the HDA. The use of a hollow shaft or a spindle weakens the structure, requires more labor and expense to manufacture, and contributes to unwanted stresses and resonances which lead to instability and additional data errors. In accordance with this invention, a HDA employs a stationary spindle, and a rotating hub to which the magnetic disks are mounted. A disk clamp is provided which has an extending portion that protrudes from the HDA housing. A conductive ground strap is coupled between the disk clamp extending portion and the housing exterior thus providing a conductive path between the rotating disks and the grounded housing, so that static charge is ef fectiveiy dissipated. The invention will be described in greater detail with reference to the drawing in which the sole figure is a schematic elevation plan view of a HDA, depicting the inventive assembly. With reference to the drawing, a HDA incorporates a solid spindle 10, made of stainless steel for example. The spindle has a central cylindrical section 10A and a lower configured section 10B which is seated on a base casting or housing 12. Surrounding the central spindle section 10A, a stator 14 is positioned, which coacts with a rotor 16 closely coupled to the stator. The rotor 16 is formed from permanent magnet material. As is well known, when electric current is supplied to the windings of the stator, the magnetic field of the rotor interacts with the flux generated by the stator windings causing the rotor to rotate. A hub structure 18, which is attached to the rotor and rotates therewith, supports one or more disks 20, so that when the rotor rotates, the hub and disks rotate accordingly. The hub structure rotates against support bearings 22 and 24. A fluidic seal 26 is located between the hub and the spindle to prevent the flow of any loose particles between the spindle area and the disk area,thus preventing damage to the disk surfaces which would result in data error. Also, since there is no airflow across bearing 24, the life of the bearing and its lubricant is extended. A cylindrical disk clamp 28 is seated on the hub structure and against the disks 20 to provide clamping pressure, so that there is no play or give that would allow undue vibration and flutter of the disks. This clamp has an extended cylindrical portion 29 of relatively small diameter which partially protrudes through an aperture 30 formed in the housing 12. To seal the HDA from the external environment, a fluidic seal 31 is provided. In accordance with this invention, a ground strap 32, which may be a resilient leaf spring made from beryllium copper or bronze, by way of example, is connected at one end to the outer surface of the housing. At the other end of the leaf spring, a connection is made to a conductive grounding button 34, which may be formed from silver graphite, for example. The button 34, which is fixed to the leaf spring, rests on the closed end or base of the cylindrical portion 29 of the disk clamp. The conductive leaf spring thereby establishes a conductive path between the grounded housing and the rotating disks, via the conductive disk clamp and rotary hub on which the disks are mounted. In this way, any static charge, which may be generated at the disk surfaces by virtue of disk rotation, is bled off and dissipated. For the purpose of simplicity and convenience, the magnetic head means and actuator for accessing the disk surfaces for recording and readout, which are conventionally provided, are not illustrated. In contrast to prior art HDA's, wherein grounding leads are disposed within the HDA housing or enclosure and brought through the bore of a hollow spindle, the configuration disclosed herein provides a simple, inexpensive grounding means and a structurally improved HDA. CLAIMS

1. A head disk assembly comprising: at least one magnetic disk a rotary hub to which said disk is mounted; means for rotating said hub and said disk; a grounded housing for enclosing said disk, hub and rotating means, a disk clamp for maintaining said hub and disk in proper alignment, said clamp formed with an extending portion; an aperture formed in said housing, said clamp extending portion protruding through said aperture; and grounding means disposed externally to said housing for establishing a conductive path between said housing and said disk, whereby static charge generated at said disk is effectively dissipated.

2. A head disk assembly as in Claim 1, wherein said grounding means comprises a leadf spring and a conductive button, and said spring at one end contacts said button, and at the other end contacts the outer surface of said housing, said button being seated on said protruding portion of said clamp.

3. A head disk assembly as in Claim 2 wherein said leaf spring is formed from beryllium copper or bronze, and said grounding button is formed from silver graphite.

4. A head disk assembly as in Claim 1, wherein said rotating means comprises a stator and a rotor.

5. A head disk assembly as in Claim 4, including a centrally located spindle for supporting said stator.

6. A head disk assembly as in Claim 4, wherein said rotor is coupled to said hub for rotating said hub and said disk.

7. A head disk assembly as in Claim 1, including fluidic seal means for sealing said aperture from the ambient environment external to said housing.

8. A head disk assembly as in Claim 1, including bearings disposed between said hub and said spindle, and wherein said disk clamp nests in a bore of one of said bearings.

9. A head disk assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.