Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
1998-11-20
2001-03-06
Tupper, Robert S. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06198605
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to disk drives for storing digital information, and more particularly, to linear actuators within disk drives.
DESCRIPTION OF THE PRIOR ART
Disk drives for storing electronic information are found in a wide variety of computer systems, including workstations, personal computers, and laptop and notebook computers. Such disk drives can be stand-alone units that are connected to a computer system by cable, or they can be internal units that occupy a slot or bay in the computer system. Laptop and notebook computers have relatively small bays in which to mount internal disk drives and other peripheral devices, as compared to the much larger bays available in most workstation and personal computer housings. The relatively small size of peripheral bays found in laptop and notebook computers can place significant constraints on the designer of internal disk drives for use in such computers. Techniques that address and overcome the problems associated with these size constraints are therefore important.
Disk drives of the type that accept removable disk cartridges have become increasingly popular. One disk drive product that has been very successful is the ZIP™ drive designed and manufactured by Iomega Corporation, the assignee of the present invention. ZIP™ drives accept removable disk cartridges that contain a flexible magnetic storage medium upon which information can be written and read. The disk-shaped storage medium is mounted on a hub that rotates freely within the cartridge. A spindle motor within the ZIP™ drive engages the cartridge hub when the cartridge is inserted into the drive, in order to rotate the storage medium at relatively high speeds. A shutter on the front edge of the cartridge is moved to the side during insertion into the drive, thereby exposing an opening through which the read/write heads of the drive move to access the recording surfaces of the rotating storage medium. The shutter covers the head access opening when the cartridge is outside of the drive to prevent dust and other contaminants from entering the cartridge and settling on the recording surfaces of the storage medium.
The ZIP™ drive is presently available for workstations and personal computers in both stand-alone and internal configurations. In order to provide a version of the ZIP™ drive for use in laptop and notebook computers, the size constraints of the peripheral bays of such computers must be considered. In particular, for an internal drive to fit in the majority of laptop and notebook peripheral bays, the drive must be no longer than 135 mm. The height of the drive must be in the range of 12 mm to 15 mm. These dimensions place many constraints on the design of such a drive, and give rise to numerous design problems. The present invention addresses and overcomes one such problem.
Disk drives, for example the ZIP™ drive, often include an actuator assembly to carry read/write heads into engagement with an information storage disk. One type of actuator is a linear actuator that includes a coil mounted to a carriage, a magnetic flux outer return path assembly, two inner return path assembly members, and two actuator magnets that are typically bonded to opposing inner walls of the outer return path. The inner and outer return paths form a flux return path for a magnetic field generated by the magnets. The magnetic flux within the air gap between the magnets and the inner return paths induces a force F on the actuator in response to an electric current in the actuator coil, thereby moving the carriage.
According to the well known principles developed by Faraday and Biot Savart, in a device where electric current is flowing orthogonal to the direction of magnetic flux in an air-gap, such as in a voice coil motor, the force F is the product of Bgap times L times i. Bgap is the field amplitude in the air gap in terms of flux density, L is the active length of current-carrying conductors in that air gap and i is the amplitude of current in those conductors. A coil consisting of a plurality of conductors wound along the direction of travel will necessarily interact, when energized, with the average of the magnetic field in the air-gap along the axial length of the coil.
Unfortunately, the force generated on the actuator by the magnets and coil substantially diminishes near the ends of the air gap. Curve
6
of
FIG. 4
is an illustration of the diminishing force F that is applied to the carriage near the ends of the gaps. The term D represents the distance from the end of the air gap. The ordinate of
FIG. 4
represents the air gap end. These end effects may possibly be due to loss of perpendicularity of the magnetic flux (relative to the magnet) near the end of the gaps. Regardless of the phenomenon responsible for the end effects, conventional full-size actuator assemblies typically allow for the end effects by limiting the travel of the carriage to the area within the air gap where end effects are minimal. Such limitation on carriage travel requires a longer outer return path to provide the longer air gap.
This solution to the end effect problem is feasible in full-size drives because such drives lack a constraint on overall length. However, in laptop and notebook computers such ineffective use of space is problematic. It is desirable to provide a linear actuator for a disk drive that enables the carriage to utilize a greater portion of the air gap.
The linear actuator has a related magnetic problem that is also exasperated by the trend toward smaller disk drives. Magnetic flux from the magnets cannot be confined to a given location or magnetic path because a portion of the flux naturally takes paths that are external to the magnet. The portion of the flux that leaks from the desired paths is referred to as leakage or leakage flux. Magnetic leakage is troublesome in magnetic disk drives because the leakage may interfere with the recording or reading of the information, or may even cause bulk erasure of magnetic information.
To ensure proper operation, it is desirable to maintain a magnetic leakage flux limit of approximately 10 Gauss in the area where the heads access the magnetic information. Conventional disk drives, in which overall drive length is not tightly constrained, may reach such a low level of leakage flux in the area of the magnetic information by locating the magnets far away from the disk and locating the read/write heads at the end of long actuator arms.
Because of the reduced drive length compared with larger drives, a linear actuator of laptop and notebook computer drives must be positioned significantly closer to the magnetic information on the disk. Because the magnets are affixed within the linear actuator, the magnets of these smaller drives must also be closer to the magnetic information. It is desirable to provide a device that diminishes the leakage flux from the actuator magnets in the area of the magnetic information on a magnetic disk, especially in smaller disk drives such as those of laptop and notebook computers.
The foregoing and other objects, features and advantages of the invention will become evident hereinafter.
SUMMARY
The present invention is directed to a disk drive having a return path geometry that enhances the uniformity of force applied to a linear actuator carriage near the ends of its travel. The return path geometry forms a gap, through which the carriage coil travels, that defines a gap narrow portion on each end. The gap narrow portion provides increased force to be generated on the carriage at the ends of the gap. Such an increase in force counteracts the typical decrease in force (compared with a gap middle portion) present at the ends of the gap.
As the actuator travels closer to the end of the gap within the narrow gap portion, the force generated on the carriage decreases. Preferably, throughout most of the gap narrow portion, the narrow gap provides an increase in force above the force generated at the gap middle portion. At the end of the gap, the force preferably is near or just below the
Briggs John C.
Wasson Ken G.
Iomega Corporation
Tupper Robert S.
Woodcock Washburn Kurtz Mackiewicz & Norris LLP
LandOfFree
Return path geometry to enhance uniformity of force on a... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Return path geometry to enhance uniformity of force on a..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Return path geometry to enhance uniformity of force on a... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2507131