GB2170359A

GB2170359A - Disc drive rotary actuator

Info

Publication number: GB2170359A
Application number: GB08601750A
Authority: GB
Inventors: Henry B Hazebrouck
Original assignee: Priam Corp
Current assignee: Priam Corp
Priority date: 1985-01-25
Filing date: 1986-01-24
Publication date: 1986-07-30
Also published as: JPS61221567A; DE3601845A1; GB8601750D0

Abstract

A disc drive rotary actuator (10) is disclosed which includes a unitary support structure (16 and 20) for supporting both a plurality of magnets (18 and 22) in spaced relationship and for supporting a pivot block assembly (30). The unitary support structure (16 and 20) may comprise a single investment cast piece or two separate investment cast pieces which are bonded together. Recessed portions are formed in the investment cast structure to receive magnets (18 and 22) in spaced relationship. One side of the support structure is closed by magnetic shields (66 and 68) whereby the actuator can be placed in close proximity to magnetic recording discs without stray magnetic flux adversely affecting stored data on the discs. <IMAGE>

Description

SPECIFICATION Disc drive rotary actuator This invention relates generally to actuators for use in magnetic disc drives, and more particularly the invention relates to a rotary actuator.

Discs having magnetic coatings on the surfaces thereof provide memories for bits of data which can be randomly accessed at high speed for either retrieving or storing data. Typically, the readtwrite heads are mounted on support arms with each read/ write head having a small pickup coil which is rapidly moved across a disc surface while the disc is spinning for detecting or storing data in concentric data tracks on the disc surface. The heads ride on a thin layer of air created by the spinning disc with the heads being in close proximity to but spaced from the disc surface.

The actuators for the pickup heads can move the head arm assembly linearly across the disc surfaces or rotatably across the disc surfaces. A linear motor is disclosed in U.S. Patent No. 4,305,105. A rotary actuatortypically has one structure to support the pivoting assembly and associated bearings which allow movement of the pickup heads and another structure to support the magnets of the linear motor and form the magnetic circuit. The magnet support structure is often composed of multiple parts which are bolted to the bearing support structure to form the final assembly. Another conventional design integrates the magnetic and bearing structures, but the integrated structure is fabricated from several parts which must be produced separately and bolted together.

The present invention is directed to a rotary actuator which has a unitary support structure for both the bearings and the magnets.

In accordance with the present invention, a disc drive rotary actuator comprises a unitary support structure for supporting a plurality of magnets in spaced relationship and for supporting a pivot block assembly, a plurality of magnets positioned in and supported by said support structure, a plurality of bearings mounted in said support structure, a shaft rotatably mounted in said bearings, and a pivot block assembly mounted on said shaft for rotation therewith, said pivot block assembly including a coil extending from one side of said pivot block assembly and positioned between said plurality of magnets, and at least one pivot head support arm extended from the opposite side of said pivot block assembly for positioning pickup heads.

An example of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective of a rotary actuator and disc drive in accordance with one embodiment of the invention.

Figure 2 is a top plan view partially in section illustrating the pivot block assembly of the actuator of Figure 1.

Figure 3 is an exploded perspective view of the rotary actuator of Figure 1.

Referring now to the drawings, Figure 1 is a perspective view of a rotary actuator shown generally at 10 in accordance with one embodiment of the present invention for accessing and storing data on a plurality of discs 12 mounted on a spindle 14. The rotary actuator 10 includes a first support structure 16 which accommodates magnets 18 and a second support structure 20 which supports magnets 22. The support structures 16 and 20 may comprise two pieces which are welded or brazed together to form a unitary structure. Alternatively, the structures 16 and 20 can be investment cast as a single piece. Preferably, recesses are formed in the support structure to receive the magnets which are affixed therein by suitable means such as epoxy.

Final machining of bearing bores is performed after the unitary structure is formed.

The support structure supports a pivot block assembly which is illustrated in the top view partially in section of Figure 2 and in the exploded perspective view of Figure 3. The pivot block 30 fits over a bearing support shaft 32 and is fastened by bolts 33 which deform the blocks slightly to ensure an intimate fit with the shaft. Shaft 32 is mounted by bearings 56 and 58 in the support structure. The head arms 34 preferably fit into dovetail slot 36 on one side of the pivot block. On the opposite side of the pivot block 30 is a coil holder 38 in which a coil 40 is mounted by suitable means such as epoxy. The coil holder 38 is preferably a separate piece which is fastened to the pivot block by means of bolts 42. The coil 40 is flat and is suitable for a low profile drive.

Mounted to one end of the arms 34 are pickup head assemblies 44 including flexures 45 and heads 46. Preferably, two pickup head assemblies 44 are mounted on opposing sides of each arm 34 with the heads 46 being generally coplanar and in staggered alignment. This allows closer spacing of the arms in the pivot block 30. Electrical leads 48 connect the heads 46 with a ribbon cable 50 which in turn plugs into an electronic circuitry of the disc drive (not shown).

Bearings 56 and 58 along with washer 59 are received in the support structure 16 and 20, respectively, and the ends of shaft 32 are positioned in the bearings. Bearing cap 60 is fastened by screws 62 to structure 20. As above described, the support structures 16 and 20 can be investment cast as a single piece or cast as separate pieces and then welded or brazed together. Alternatively, powdered metal technology can be employed in fabricating the support structure. Advantageously, the bearings and a shaft and the pivot block can be readily assembled in the unitary support structure.

In operation, energization of the coil 40 which is positioned between the magnets 18 and 22 causes a rotation of the pivot block and head arm assembly thereby moving the pickup heads across the surface of the discs. The magnets 18 and 22 are positioned in the support structure to provide a magnetic path through the support structure and across an air gap between the magnets in which the coil is positioned.

A magnetic shield comprising members 66 and 68 of the support structure prevent stray magnetic flux from adversely affecting data stored on the surfaces of the magnetic discs.

A rotary actuator having a unitary support structure in accordance with the invention eliminates the need of multiple parts in the magnet and pivot block support structure. The actuator is more readily manufactured and assembled, and the unitary structure provides an improved flux path with a flux shield integrated therewith.

Features of the disc drive rotary actuator described above are also described and claimed in U.K. Applications Nos. (Agents References: BA6937, BA6939 and BA6940).

Claims

1. A disc drive rotary actuator comprising a unitary support structure for supporting a plurality of magnets in spaced relationship and for supporting a pivot block assembly, a plurality of magnets positioned in and supported by said support structure, a plurality of bearings mounted in said support structure, a shaft rotatably mounted in said bearings, and a pivot block assembly mounted on said shaft for rotation therewith, said pivot block assembly including a coil extending from one side of said pivot block assembly and positioned between said plurality of magnets, and at least one pivot head support arm extended from the opposite side of said pivot block assembly for positioning pickup heads.

2. A disc drive rotary actuator as claimed in Claim 1 wherein said unitary support structure provides a magnetic path for said magnets.

3. A disc drive rotary actuator as claimed in any preceding claim wherein said support structure includes a magnetic shield on one side whereby said actuator can be placed in close proximity to magnetic recording discs without stray magnetic flux adversely affecting data stored on the discs.

4. A disc drive rotary actuator as claimed in any preceding claim wherein said unitary support structure includes recessed portions for receiving said magnets.

5. A disc drive rotary actuator as claimed in any preceding claim wherein said unitary support structure comprises a single investment cast piece.

6. A disc drive rotary actuator as claimed in any of Claims 1,2,3 and 4 wherein said unitary support structure comprises two investment cast pieces which are bonded together.

7. A disc drive rotary actuator as claimed in any of Claims 1,2,3 and 4 wherein said structure comprises two pieces fabricated using powdered metal and then bonded together.

8. A disc drive rotary actuator substantially as herein described with reference to the accompanying drawings.