Patent Application
20050286173
This application relates generally to movable actuators and more particularly to a crash stop assembly for a movable actuator.
In an apparatus such as a disc drive, information is written to and read from tracks on data storage device discs through the use of a pivoting actuator assembly. The actuator assembly includes heads, which each move in close proximity above the corresponding surface of the associated disc. A voice coil motor controls the track position of the heads by pivoting the actuator assembly. The voice coil motor typically includes a coil attached to the actuator assembly, as well as one or more permanent magnets, which establish a magnetic field in which the coil is immersed. A bottom pole proximal the data storage device base plate and a top pole distal from the base plate typically establishes the magnetic field. The controlled application of current to the coil causes magnetic interaction between the permanent magnets and the coil so that the actuator assembly pivots.
Various approaches have been developed to securely position an actuator assembly in such an apparatus during a loss of power event or shutdown of the drive such that the heads do not land on a portion of the disc real estate that contains data. Typically these approaches involve either positioning the actuator assembly onto a shelf to hold the heads away from the discs or positioning the heads over portions of the disc surfaces that contain no data, such as the landing zones of the discs. The landing zones typically contain no magnetic recorded information or alternatively contain only historical servo information that is not pertinent to drive operation if damaged by the heads actually contacting the surfaces of the discs in this location. Approaches for holding the arm assembly in such as “park” position include mechanical latches, electromechanical latches and magnetic latches.
To limit the range of motion of the actuator and heads under loss of power conditions and keep the heads in the landing zone, designers usually incorporate crash stops and a latch mechanism to position and hold the arm in the park position while the drive is without power. One concern in providing a latch and crash stop assembly is the level of energy absorbed by the crash stops. It is desirable that the crash stops absorb the impact of the actuator assembly as it stops without detrimentally affecting the head disc interface, even though the actuator assembly is designed to stop in a position away from the data region of the discs where the heads are parked. If excessive impact were to occur, the heads or the disc surface itself could be damaged by head slap. In addition, the actuator arm inertia and the impact energy varies depending on the individual deck design. This generally requires separate crash stop design to accommodate the change in impact energy, thereby increasing design and tooling costs.
Accordingly, there is a need for a crash stop assembly with uniform design able to provide varying degrees of stiffness. The present invention provides a solution to this and other problems, and offers other advantages as well.
One embodiment of the present invention may be viewed as an apparatus in which a pivotally supported actuator assembly mounted on the base plate, and one or more rotationally adjustable crash stops for limiting pivotal movement of the actuator assembly. Alternatively, the crash stops may be located in the base of the actuator assembly which is then attached to the data storage device base plate.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.
Referring to
During a seek operation, the track position of the heads 122 is controlled through the use of a voice coil motor 124, which typically includes a coil 126 attached to the motor aspect 116 of the actuator assembly 110, as well as one or more permanent magnets 128, which establish a magnetic field in a gap in which the coil 126 is immersed. The magnetic field is typically established through a bottom pole plate 130 mounted on the base plate 102, which includes a permanent magnet 128 thereon, and a top pole 132, shown partially cut away, spaced from the base plate 102, which also includes a permanent magnet 128. The controlled application of current to the coil 126 causes magnetic interaction between the permanent magnets 128 and the coil 126 so that the coil 126 moves back and forth in the gap between the magnets 128 in accordance with the well-known Lorentz relationship. As the coil 126 moves, the actuator assembly pivots about the bearing shaft assembly 112, and the heads 122 are caused to move across the surfaces of the discs 108.
The spindle motor 106 is typically de-energized when the data storage device 100 is not in use for extended periods of time. The heads 122 are moved over park zones or landing zones 123 near the inner diameter of the discs 108 when the drive motor is de-energized. The heads 122 are secured over the park zones 123 through the use of an actuator latch arrangement (not shown), which prevents inadvertent rotation of the actuator assembly 110 when the heads are parked. A crash stop assembly 140 limits pivotal movement of the actuator assembly 110. Alternatively, or in addition, the data storage device may comprise a crash stop located on the opposite side of the actuator assembly to limit the outward movement of the heads 122. Such a design may be desirable, for example, where the parking zone consists of a ramp located adjacent the outer periphery of the discs 108.
Alternatively, the bottom portion of the stem 150 may be substantially cylindrical in shape. In this manner, the crash stop could be rotated to essentially any position within the 360 degree arc defined by the aperture. The aperture 115 in this case would be a smooth bore and the stem may be smooth to allow for limitless rotation. In this alternative embodiment, a securing means (not shown) would be needed to secure the crash stop in the desired position. Alternatively, the surfaces of the stem and aperture may comprise small flexible teeth that engage one another and allow position change by “clicking” from one rotational position to the next. Alternatively the teeth may also be inflexible, i.e. closely spaced splines that intermesh such that the crash stop must be rotated to the selected position, and then inserted into the complementary shaped aperture such that the teeth or splines are engaged and the crash stop cannot be further rotated while in this engaged position.
It will be clear that the present invention is well adapted to attain the ends and advantages mentioned as well as those inherent therein. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the invention disclosed and as defined in the appended claims.
