GB2342762A

GB2342762A - Hard disk drive actuator arm has magnetic latch formed from the base plate of the actuator support

Info

Publication number: GB2342762A
Application number: GB9923967A
Authority: GB
Inventors: Kelly Williams; Tho Pham; Anh Hoang
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1998-10-12
Filing date: 1999-10-11
Publication date: 2000-04-19
Anticipated expiration: 2019-10-11
Also published as: GB9923967D0; GB2342762B; DE19949155B4; DE19949155A1; KR20000028988A

Abstract

The hard disk drive actuator arm 30 can be latched with the read/write heads 26 in the parking zone. The latch 46 is formed as part of the supporting base plate 36 and engages with a tab 52, and optionally a pin 50, mounted on the actuator. The latch portion has a predictable magnetic force which maintains the position of the actuator and the heads. A method of manufacture is also disclosed.

Description

2342762 MAGNETIC LATCH The present invention relates generally to magnetic

media data storage devices, and more particularly, to a_ latch for a voice coil motor of a hard disk drive. The disk drive may have a single disk or several disks.

Generally, a disk drive comprises a disk recording medium of magnetic material and an actuator which travels over the surface of the disk. The actuator is used to position a transducer head (ie a read/write head) over the disk surface. The actuator is a delicate piece of electronic equipment containing a number of electronic and optical devices. It is therefore necessary to provide means to lock the actuator in a pre-determined position during transportation or servicing of the equipment in order to prevent accidental /shock damage to the actuator and/or the magnetic disk.

Conventionally, locking of the actuator during periods of non-operation has been achieved by moving the actuator to a predetermined position and latching it in, that position. The latching position is known as the landing zone and is usually an inner position of the disk. The actuator latch typically engages the actuator due to a permanent magnetic field or due to a solenoid- generated magnetic field. In this way the heads are moved away from the data fields of the disk to prevent corruption of data. It is desirable to secure the actuator to ensure that the heads 'do not move into the data fields of the disk when the drive is powered down. 30 The latch is usually formed as a separate molded part which has either been manufactured by a powdered metal process or a metal injection molding (MIM) process. A disadvantage of the metal injection process is

2 that it is relatively expensive to operate and the capital costs of the. equipment are high. For this reason, there is only a small number of production facilities throughout the world which are able to perform this process. Furthermore, it can be difficult to achieve high dimensional tolerances when seeking to mold a latch to fit to the support for the actuator arm. This in turn.means that the latched position of the actuator arm may not be well defined. Corresponding tolerances therefore arise in the position of the landing zone leading to wasted space on the disk which cannot be used for data storage.

Although the powdered metal process for forming latch is relatively inexpensive it also suffers the is disadvantage that it is difficult to manufacture the latch to very high tolerances. This is due in part to dimensional changes which inevitably occur during the sintering process. Furthermore, there is also the problem that sintered parts may be prone to varying latching forces perhaps because of inhomogeneities in the. permanent magnetic field, as a result of dimensional changes on sintering, or as a consequence of natural product variability from the sintering process.

It is therefore an object of the present invention to provide a latch which reliably engages an actuator arm of a disk drive.

It is a further object that the position of the latch, and hence the position of 'the landing zone, be defined with higher precision than is currently possible in the prior art mechanisms. This has the benef it of increasing the useful area of the disk.

It is another object of the present invention to provide a simplified latch mechanism and a simplified 3 means of forming the latch. It is thus an object to provide an inexpensive and easy to manufacture latch for a disk drive.

According to the one aspect of the present invention, there is provided an actuator support comprising: (a) means for moveably mounting an actuator on a base; (b) means for providing a magnetic field operative to displace the actuator; and (c) a latch; wherein the latch is formed as part of the actuator support.

According to another aspect of the present invention, there is provided an assembly comprising an actuator support as described above and an actuator, wherein the actuator includes means for providing a magnetic field and a tab for removably engaging with the latch.

According to a further aspect of the present invention, there is provided a method of constructing an actuator support, the method comprising the steps: (a) providing an actuator support including a base which is, substantially planar; and (b) forming a latch by bending a portion of the base out of the plane of the base to form a projection.

In general, the present invention is concerned with providing a latch for an actuator so that the latch forms an integral part of the supporting structure for the actuator. Thus the invention is concerned with avoiding the need to form separately a latch which must then be fastened to the supporting structure. In this manner, it is possible to reduce the tolerances to a level below these of conventional latch assemblies.

It is possible for the whole supporting structure to be formed by metal injection molding or by conventional 4 powdered metal processes. However, on the basis of cost and dimensional accuracy it is preferred, that the supporting structure is formed from sheet material, for example magnetic steel or another magnetic alloy, with 5 the latch being formed therefrom.

The number of magnetic recording heads and associated disks is not essential to the working of the invention.

one embodiment of the present invention concerns a latch which can be used in conjunction with a voice coil motor of a hard disk drive. The actuator is usually formed as an arm and includes a conventional voice coil motor which includes a magnet that is supported by a magnet plate. The magnet is located adjacent to the voice coil that is attached to the actuator arm. The actuator arm supports a number of magnetic recording heads that read and write information from a plurality of rotating magnetic disks.

In a preferred embodiment of the present invention, a portion of the supporting structure for the actuator arm ie the planar base is bent to create an integrated latch. The latch is thus a part of the same material as the base. The supporting structure (base) is usually a magnetic plate and the actuator arm is usually secured to the supporting structure by means of a fixing which allows a pivoting movement of the actuator arm in response to the voice coil. In this manner, the transducer on the actuator arm is Lble to move over the surface of the disk as the arm pivots about the fixing.

The latch of the present invention reduces the tolerances associated with manufacturing the latch housing, and thus, reduces the costs of producing the disk drive. It also enables a larger part of the disk to be used for data storage compared with the prior art systems.

The actuator arm may include a tab, and may optionally include a pin, that engages the latch when the heads are moved to a landing zone of the disks. The tab is simply that part of the actuator arm which engages with the latch and may or may not be formed as a projecti,on from the actuator arm. The latch has a magnetic force which holds it (and the pin when present) and maintains the position of the actuator arm and the heads.

Furthermore, the magnetic force that the latch exerts on the actuator arm, and pin when present, can be determined and provides a predictable latching force for is each disk drive.

In an embodiment, the magnitude of the latching force can be varied by varying the size of the latch. In another embodiment the position of the latch relative to the fixing point (which is usually a pivot) of the actuator arm may be varied to vary the effective moment, on the actuator arm about the fixing. In a further embodiment, the slots or cuts used to form the latch housing may be cut in a radial direction relative to the centre of the disk ie in a direction which is substantially parallel to the longitudinal axis of the actuator when mounted for use, or in a direction which is similar to the circumferential direction of the disk. This allows control of the orieHtation of the latch relative to the supporting structure. The orientation of the latch may be chosen according to the desired configuration of the actuator arm and/or the amount of magnetic force which is to be available to engage the actuator arm.

6 In a further embodiment, additional means may be provided on the latch housing to supplement or vary the degree of magnetic force, such means including a permanent magnet or even a solenoid. However, such means S whilst beneficial in adding a further degree of control also add to the complexity and cost of the invention.

The present invention will now be described, by way of examp.le only, with reference to the following drawings in which:

Figure 1 is a perspective view of a voice coil motor for a hard disk drive according to the prior art;

Figure 2 is a perspective view of a latch according to the present invention engaging an actuator; and Figure 3 is an enlarged view showing an latch formed from a magnet plate according to the present invention.

In the drawings, Figure 1 shows a typical hard disk drive and actuator arrangement of the prior art. In this arrangement, the actuator is latched to latch housing 9 due to a magnetic field as discussed below. The disk drive includes a plurality of magnetic recording heads 1, located adjacent to a number of rotating magnetic disks 2. The recording heads 1 are mounted to flexible arms 3 which are attached to an actuator arm 4. The actuator arm 4 can pivot about a bearing assembly 5 to move the heads 1 across the surfaces of the disks 2.

A voice coil 6 is attached to the actuator arm 4 adjacent to a magnet 7. The magnet 7 is supported by a magnet plate 8 that is mounted to!:he base plate of the disk drive. Although not shown, the disk drive may also have a magnet and corresponding magnet plate above the voice coil 6. The voice coil 6 is attached to an electrical circuit (not shown) which provides a current to the coil 6 to move the actuator arm 4 and heads 1, as 7 is well known in the art.

As shown in Fig. 1, a prior art disk drive may have a latch housing 9 that cooperates with a pin 10 of the actuator arm 4 to latch the heads 1 into the landing zones of the disks 2. When the disk drive is powered down the latch housing 9 has enough magnetism originating from the magnet 7 to hold the pin 10 and secure the actuator arm 4.

The latch housing 9 is typically a separately molded part manufactured by either a powdered metal process or a metal injection molding (MIM) process. The latch housing 9 is typically mounted to the magnetic plate with a pin that is inserted into a corresponding oblong slot in the plate.

The latch assembly introduces a number of manufacturing tolerances which reduce the accuracy of the head location within the landing zone of a disk. Consequently, the landing zones must be wide enough to compensate for the inaccuracy of the head location. A wider landing zone reduces the data fields of the disks.

Figure 2 shows a portion of a hard disk drive 20 using a latch according to the present invention. The disk drive 20 includes a number of magnetic disks 22 that are rotated by a spin motor 24. Adjacent to each surface 27 of the disks 22 are a plurality of magnetic recording heads 26. The heads 26 write and read information stored on the surfaces 27 of the disks 22. Each recording head 26 is mounted to a flexible arm 28.' Each flexible arm 28 is attached to an actuator arm 30 that pivots about a bearing assembly 32. The bearing assembly 32 pivots the actuator arms 32 for moving the heads 26 across the surfaces 27 of the disks 22 for writing data into, or reading data out of, the disks 22.

8 A voice coil 33 is attached to the end of the bearing assembly 32. The voice coil 33 is located adjacent to a magnet 34. The magnet 34 is mounted to a magnet plate 36 that is attached to a base plate (not shown) of the disk drive by screws 38. The voice coil 33 may also be adjacent to a top magnet 39 that is mounted to a top magnet plate 40. The top plate 40 is separated from the bottom plate 36 by spacers 41. The voice coil 33 is connected to an electrical circuit (not shown) which provides a current to the coil 33 to move the actuator arm 30 and heads 26, as is known in the art.

As shown in Figure 3, the bottom magnet plate 36 has a top surface 42, an opposite bottom surface 44, and a bent latch portion 46 which extends above the top surface 42. The latch portion 46 is constructed by initially stamping a pair of slots 48 into a metal plate comprising the magnet plate 36. The slots could equally be formed by cutting or any other conventional metalworking process. The slots 48 are separated by a cantilevered tab which is bent upwardly to form the latch 46. The, slots 48 provide stress relief for the latch portion 46, such as when the latch portion 46 is engaging a metal pin 50. The latch portion 46 is typically bent into a position that is essentially perpendicular to the top surface 42 of the plate 36. In this case, it will be seen that the slots are bent in a direction which is towards the centre of the disk and the slots are parallel. However the slots need not be parallel. It is also equally possible for the one or more slots to be provided in a direction which is similar to the circumferential direction of the disk. The resulting tab can still be bent upwards to form a latch.

Referring again to Fig. 2 and Fig. 3 of the 9 drawings, the latch portion 46 engages a metal pin 50 that is pressed into a tab 52 of the actuator arm 30. The metal pin 50 may be in the form of a screw and be adjustable. Equally, the pin 50 may be omitted so that tab 52 itself engages with the latch portion 46. The magnet plate 36 and latch portion 46 are typically constructed from a steel material that provides a magnetic force sufficient to attract and hold the tab or the metal pin 50, to secure the actuator arm 30 to the latch portion 46.

In operation, when the disk drive 20 powers down, the electronics of the drive 20 provide a current to the voice coil 33 to move the heads 26 to a landing zone at the inner diameter of each disk 22. Rotation of the actuator arm 30 moves the pin 50 into engagement with the latch portion 46 of the present invention. When power is terminated to the drive, the latch portion 46 provides a magnetic force that holds the pin 50 to the latch portion 46 for securing the heads 26 at the landing zone of each disk 22.

Providing an integrally-formed bent latch portion reduces the tolerances and assembly cost associated with producing the disk drive. The reduction in tolerances reduces the width of the landing zone and increases the data field of each disk 22. Additionally, the bent latch assembly is relatively inexpensive to produce and provides a predictable latching force for each disk drive. I It is also possible to control the amount of magnetic force required for latching by varying the size and/or position of the latch. There is even the possibility of adjusting the latched position of the actuator to control the position of the landing zone once the position of the latch has been f ixed. This may be useful in cases in which the disk unit is fixed within the equipment separately from the unit containing the actuator and latch so that some degree of adjustability is desirable.

Claims

1. An actuator support comprising:

(a) means for moveably mounting an actuator on a base; (b) means for providing a magnetic field operative to displace the actuator; and (c), a latch; wherein the latch is formed as part of the actuator support.

2. An actuator support as claimed in claim 1, wherein the base is substantially planar and the latch is formed as a projection from the base.

3. An actuator support as claimed in claim 2, wherein the base includes one or more slots and the projection is formed from material between the or each slot and/or between the slot and the perimeter of the base.

4. An actuator support as claimed in claim 3, wherein the slots are in a direction which is substantially parallel to the longitudinal axis of the actuator when mounted for use.

5. An actuator support as claimed in any preceding claim, wherein the means for'providing a magnetic field is a permanent magnet.

6. An actuator support as claimed in any preceding claim, wherein the means for moveably mounting the actuator is a pivot.

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7. An assembly comprising an actuator support as claimed in any of claims 1 to 6 and an actuator, wherein the actuator includes means for providing a magnetic field and a tab for removably engaging with the latch.

8. An assembly as claimed in claim 7, wherein the tab I includes a pin and it is the pin which removably engages with the latch.

9. An assembly as claimed in claim 8, wherein the position of the pin is adjustable relative to the tab so that the latched position of the actuator may be adjusted by adjusting the position of the pin.

10. A method of constructing an actuator support, the method comprising the steps:

(a) providing an actuator support including a base which is substantially planar; and (b) forming a latch by bending a portion of the base out of the plane of the base to f orm. a projection.

11. A method as claimed in claim 10, further including before step (b) the step of forming one or more slots in the base.

12. A method as claimed in claim 11, wherein the or each slot is formed in a direction which is substantially parallel to the longitudinal axis of the actuator when mounted for use.

13 13. An actuator support substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.

14. An assembly substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.

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15. A method substantially as hereinbefore described with reference to Figures 2 and 3 of the accompanying drawings.

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