Magnet assembly apparatus

An assembly apparatus for a magnet assembly is disclosed. The assembly apparatus includes first and second assembly nests and an assembly slide operable between an advanced position relative to the assembly nests and a retracted position for assembly. As disclosed the assembly apparatus is used to assemble spacer posts between opposed magnet/backiron assemblies. The assembly apparatus includes spacer nests proximate to the assembly nests for assembly of spacers between the opposed magnet/backiron assemblies.

FIELD OF THE INVENTION

The present invention relates to a magnet assembly. In particular, the present invention relates to a magnet assembly for a voice coil motor for a data storage device.

BACKGROUND OF THE INVENTION

A disc drive includes a plurality of stacked discs which are rotationally supported relative to a disc spindle and an actuator assembly movably supporting a plurality of data heads for reading and writing data to the discs. The actuator assembly includes an actuator drive typically a voice coil motor for actuating or positioning the heads relative to selected data tracks of the discs. The voice coil motor includes a magnet assembly defining a permanent magnetic field and an energizable coil coupled to an actuator block supporting the heads. A voltage is supplied to the coil to selectively operate and move the actuator block to align the data heads relative to predetermined data tracks of the disc.

A typical magnet assembly includes upper and lower pole plates or backirons which are supported in opposed spaced relation and at least one magnet coupled to one of the backirons to define a flux gap therebetween. An energized coil moves in the flux gap between the upper and lower pole plates and the magnet. For proper operation of the voice coil motor, magnets must be accurately aligned and assembled to upper and lower pole plates; and upper and lower pole plates should be accurately aligned and connected for accurate head placement relative to selected data tracks. The magnetic flux or force of the magnetic components makes it difficult to handle and assemble magnets relative to upper and lower pole plates. The attraction force between magnetic components must be controlled for placement and assembly of magnets and pole plates. The present invention addresses these and other problems, and offers advantages over the prior art.

SUMMARY OF THE INVENTION

The present invention relates to a magnet assembly including spacers having chamfered posts insertable into post holes of opposed spaced backirons. The chamfered posts are self centering in the post holes of the backirons to assemble the magnet assembly. Pole plates or backirons can be assembled to spacers with the chamfered posts using the magnetic attractive force of the magnets supported by the upper or lower pole plates. Chamfered posts at a first end of spacers are inserted into post holes on a first backiron. A second backiron is supported spaced from the first backiron by an assembly slide to retain the second backiron against the magnetic attraction prior to assembly. The assembly slide is withdrawn so that the second backiron is attracted toward the first backiron and chamfered spacer posts are inserted into post holes on the second backiron for assembly.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present invention relates to a system and apparatus for assembling a magnet assembly100to form a flux gap102between magnetized magnets104,106and backirons108,110. Magnets104,106are supported on backirons108,110separated by spacers112,114to form flux paths115-1,115-2for operating a voice coil motor116of a disc drive118as illustrated inFIG. 2. Awound coil120is supported in the flux gap102and is connected to an E-block assembly122shown inFIG. 2to move the E-block assembly122to position data heads124relative to selected data tracks of a disc126for read or write operations. Current is supplied to the wound coil120to rotationally actuate the E-block122along an arcuate path as illustrated by arrow128for head placement relative to selected data tracks of a disc. Although a particular magnet assembly embodiment is shown, it should be understood that alternate magnet assembly embodiments including a magnet supported on one of the backirons108,110can be used to form a flux gap for operation of a voice coil motor116.

In prior magnet assemblies illustrated inFIG. 3, spacers112,114include opposed, generally flat ends130,132having fastener openings134,136. Fastener openings138,140on backirons108,110are aligned with openings134,136on spacers112,114to insert a fastener, illustrated in phantom, therethrough to connect backirons108,110in opposed spaced relation. Backiron openings138,140must be centered or aligned with spacer openings134,136for connection and assembly. The magnetic attraction between magnets104,106or magnetic components, makes it difficult to control alignment and placement of the openings for assembly. Thus, openings were typically manufactured with large tolerance dimension for easier alignment and connection of the backirons to the spacers. Higher powered magnet assemblies are particularly difficult to assemble and typically required expensive tools and devices to align and assemble the backirons without damaging the magnets.

The present invention relates to a self centering or aligning assembly for magnetic components. In the embodiment illustrated inFIG. 4, a magnet assembly140includes spacers144,146which support backirons148,150in opposed spaced relation. Backirons148,150support opposed magnets152,154which are magnetically attracted toward one another. As shown inFIG. 4, spacers144,146include opposed chamfered posts156-1,156-2having chamfered ends which are sized for insertion into post holes158,160on backirons148,150. The chamfered portion of posts centers posts156for insertion into post holes158,160for assembly. In the embodiment illustrated inFIG. 4, post holes158extend through the width of backiron148so that spacer posts156-1are connected to chassis162via a threaded fastener (not shown) in threaded bore164of posts156-1. Although a particular embodiment is shown for post holes and a particular spacer shape is shown, it should be understood that post holes can extend partially through or entirely through the width of the backiron and that various shaped and sized spacers can be used to support backiron148,150. Further, application is not limited to the particular assembly shown including magnets152,154on both backiron148,150and can be applied to alternate magnet assembly arrangements.

For assembly, the magnetic attraction between opposed backiron-magnets is used to assemble the magnetic components. Posts156-1are inserted into post holes158of backiron148. Backiron150is positioned relative to backiron148and spacers144,146so that posts156-2align with post holes160. Once aligned, the magnetic attraction between opposed backiron-magnets is used to assemble posts156-2of spacers144,146into post holes160of the backiron150. The chamfered posts156-2self-align the posts156-2relative to post holes160so that posts156-2are inserted into lost holes160while the backiron150is attracted toward backiron148and spacers144,146.

FIGS. 5-6schematically illustrate an assembly embodiment for backirons148,150and spacers144,146. As shown, assembly nests170,172and spacer nests174,176support assembly components. Assembly nest170holds backiron-magnet148,152and assembly nest172holds backiron-magnet150,154. Spacer nests174,176hold spacers144,146and are opened to assembly nests170,172to insert spacer posts156into post holes158,160. Assembly nest170includes a nest floor180and assembly nest172includes a nest table182elevated above floor180. Table182is elevated above floor180to contain backiron150in opposed spaced relation to backiron148as illustrated in FIG.6. The separation between table182and floor180corresponds to the height of the spacers144,146so that when spacer posts156are inserted into post holes158,160, the opposed backiron-magnets148,152and150,154are supported relative to the floor180and table182of assembly nests170,172, respectively.

Prior to assembly, backiron-magnet150,154is elevated or supported above the table182via an assembly slide184as illustrated in FIG.5. Slide184operates between a pre-assembly position and an assembly position. In the pre-assembly position, slide184is in assembly nest172to support backiron-magnet150,154above table182and in the assembly position, slide184is retracted from the assembly nest172so that the backiron-magnet150,154is magnetically attracted toward the backiron-magnet148,152and drops into assembly nest172for assembly. Alternate assembly embodiments can be employed to conform assembly nests170,172and spacer nests174,176for use for alternate magnet assembly designs.

FIGS. 7-13are more detailed illustrations of an assembly embodiment200for backirons148,150and spacers144,146. Device200includes a base202, assembly nests204,206and spacer nests208,210. As shown, assembly nests204,206and spacer nests208,210are cooperatively formed via assembly blocks212,214. Assembly blocks212,214are coupled to base202so that base202forms a floor of the assembly nest204for backiron-magnet148,152.

In the embodiment shown, assembly block212is fixedly supported relative to base202and assembly block214is rotationally supported relative to base202via shoulder screw218. Assembly block214rotates as illustrated by arrow220between an opened position relative to assembly block212for loading components into assembly nest204and a closed position relative to assembly block212for assembling components. Latch222is rotationally connected to base202as illustrated by arrow224to lock assembly block214in the closed position. Although a particular rotational arrangement is shown, application is not limited to the particular arrangement shown. For example, assembly blocks212,214can be slidably supported relative to base202to operate between an opened position and closed position.

Assembly blocks212,214include channels226-1,226-2formed25between opposed spaced stepped rails228-1,228-2,230-1,230-2and232-1,232-2,234-1,234-2. A portion of channels226-1,226-2and rails230-1,230-2,232-1,232-2form a backiron-magnet table for assembly nest206. In the embodiment shown, table includes a magnet well portion formed by channel226for magnet154and a backiron shelf formed by rails230,232for supporting the backiron. As shown, an assembly slide236moves along a track formed by channel226-1,226-2between a pre-assembly position and an assembly position as illustrated by arrow238.

In the pre-assembly position, slide236is located in the assembly nest formed by portions of channels226-1,226-2of assembly blocks212,214to support backiron-magnet above the assembly nest table to load the backiron-magnet. For assembly, slide236is retracted out of assembly nest206so that backiron-magnet is supported by the assembly nest table with backiron supported by rails232-1,232-2and magnet extending into the magnet well formed by portions of channels226-1,226-2. Thus, as described, assembly slide236elevates backiron-magnet150,154above spacers144,146and backiron-magnet148,152prior to assembly and is withdrawn so that backiron150drops down into assembly nest206and is attracted toward backiron148to assembly spacers144,146between backirons148,150. In the embodiment described, assembly nests204,206include a backiron portion and a magnet well portion for a magnet assembly including opposed magnets152,154supported by backirons148,150, although application is not limited to the particular assembly nest configuration shown.

FIG. 8is an exploded view of the embodiment of FIG.7. As shown, base202includes base plate240having feet242connected thereto and extending therefrom. Base plate240also includes magnet cavities244-1,244-2. Magnets246-1,246-2are supported in cavities244-1,244-2to secure backiron-magnet in assembly nest204to limit movement of the backiron-magnet150,152. Preferably, the depth of the cavities244-1,244-2is sufficient so that bias magnets246-1,246-2are recessed 0.0002-0.0003 inches below an upper surface of plate240for clearance. Preferably, magnets246-1246-2are glued into cavities244-1,244-2using a cyanocrylic adhesive.

In particular, assembly nest204,206and post nests208,210are sized within tolerance dimensions to accommodate backiron assemblies and posts. The tolerance dimensions of the nests204,206and post nest208,210is such that the backiron assemblies and posts can move or shift position in the nests. Movement of the backiron assemblies in the nests can make it more difficult to insert posts156into post holes. Thus, as described, bias magnets246-1,246-2secure backiron-magnet148in assembly nest204to limit movement of backiron-magnet148,152in assembly nest204after assembly of block214is closed for insertion of spacer posts156into post holes158on backiron-magnet148,152. The magnets246-1,246-2also attract spacers144,146and backiron148to hold spacers144,146and backiron148secure during the merge or assembly of components for the magnet assembly.

In the embodiment shown, assembly slide236includes an elongated slide plate250having a width sized for insertion in channels226-1,226-2and a thickness sized to elevate backiron-magnet150,154above the nest table and backiron-magnet148,152. Slide plate250is slidably secured in channel226via a slide block252secured to assembly block212. Slide block252includes a post254which extends into an elongated slot256on slide plate250. Slide block252is secured at stepped end258,260of rails228-1,234-1as shown. Slide plate250moves along post254on slide block252for controlled movement of slide236between a pre-assembly position and an assembly position as described. As shown, slide plate250includes an opening262to grip the slide plate250to move the slide between the pre-assembly position and the assembly position. As shown, slide plate236includes a ramp264to gradually release backiron-magnet150,154for assembly.

As previously explained, assembly block214is rotationally coupled to base202via shoulder screw218.FIG. 9illustrates an embodiment of shoulder screw218. As shown, shoulder screw218includes a threaded tip265, a shank portion266and a head267. Shank portion266is sized to extend through an opening268in assembly block214to rotationally couple assembly block214to base. Shoulder screw218is secured to base202via threaded tip265. Head267is sized larger than opening268to retain assembly block214on shank portion266to rotationally couple block214to base202. Stepped edge269of shank portion266controls the depth of shoulder screw218relative to base202and provides sufficient clearance between head267and assembly block214so that assembly block214rotates as illustrated by arrow220for operation.

In the illustrated embodiment, assembly nests204,206and spacer nests208,210are cooperatively formed by opposed formed ends of assembly blocks212,214. In the embodiment illustrated inFIGS. 10-11, formed ends include contoured spacer well portions270-1,270-2,272-1,272-2and stepped nest cavity portions274-1,274-2. In the closed position, well portions270-1,270-2and272-1,272-2on assembly blocks212,214form spacer nests208,210and stepped nest cavity portions274-1,274-2on assembly blocks212,214form assembly nest204to house a backiron assembly including backiron148and magnet152. In the embodiment shown, stepped rails228,234include contoured wails276,277to form a perimeter of assembly nest206, formed by channel226and rails230,232for locating a backiron assembly. Rail230-2of block214includes notch278for magnet154clearance.

As shown inFIGS. 12 and 13, stepped nest cavity portions274-1,274-2cooperatively form assembly nest204including backiron portions282-1,282-2and magnet portions284-1,284-2to house a backiron assembly including a backiron148and magnet152. Backiron portions282-1,282-2include walls contoured to the shape of the backiron148and magnet portions284-1,284-2, include wedges286-1,286-2contoured in the shape of magnet152to limit movement of the backiron and magnet in the assembly nest204. Assembly nests204,206are contoured or shaped to accommodate various magnet and backiron designs and the present invention is not limited to any particular shape or design nor a magnet assembly including opposed backirons148,150supporting opposed magnets152,154as shown. Different assembly nests and post nests can be employed depending upon the configuration of the magnet assembly components.

FIG. 14is a flow chart of the assembly operation of the present invention. As shown, chamfered posts156are inserted into post holes158of backiron148as illustrated by block300. A second backiron is supported on an assembly slide and aligned with spacer posts156-2as illustrated by block302. Assembly slide is retracted from the second backiron so that backiron assemblies are attracted toward spacer posts144,146for assembly as illustrated by block304. Thus, as described, the backiron and magnet components are self aligning for assembly and can be assembled using magnetic attraction between the magnetic components for a simply, reliable and relatively inexpensive assembly process.

As previously described, with reference toFIGS. 7-8, the first backiron is supported in assembly nest204for assembly operations. The first backiron is loaded in assembly nest204, while slide236is in the retracted position and assembly block214is opened. For operation, assembly block214is rotated closed as illustrated by arrow220inFIG. 7to a latched position. Slide236is advanced into assembly nest206as previously described to support the second backiron. For assembly, posts are loaded into post holes and the second backiron is loaded onto slide236and aligned with posts156of spacers144,146. Thereafter, the slide236is retracted to assemble the second backiron on spacer posts. Upon completion, assembly block214is unlatched and rotated open to remove the completed assembly. As described, the nest204is operable between an opened position for loading operations and a closed position for assembly operations. Upon completion of the assembly process, assembly block214is opened to remove the completed assembly. During assembly operation, components are biased toward magnets246-1,246-2to limit movement for component alignment.

A magnet assembly100including backirons148,150supported in opposed spaced relation by spacers144,146having chamfered posts156insertable in post holes158,160of backirons148,150. For assembly, chamfered posts136are inserted into post holes158on a first backiron148. A second backiron150is supported spaced from the first backiron148by an assembly slide236to retain the second backiron150against the magnetic attraction between the first and second backirons148,150for preassembly alignment of the post holes160on the second backiron150relative to spacer posts156. The assembly slide236is withdrawn from the second backiron150so that second backiron150is attracted toward the first backiron148and spacer posts156are inserted into post holes160on the second backiron150for assembly.