1. Field of the Invention
The present invention relates to magnetic disk drives, and more particularly to a mechanism for preventing damaging contact between a magnetic head slider assembly and a rigid magnetic disk due to shock loads applied to a magnetic disk drive.
2. History of the Prior Art
Among the better known data storage devices are magnetic disk drives of the type in which a magnetic head slider assembly floats on an air bearing at the surface of a rotating rigid magnetic disk. Such disk drive are often of the so-called Winchester type in which one or more rigid magnetic disks are located within a sealed chamber together with one or more magnetic head slider assemblies. The magnetic disk drive may include one, two or more rigid magnetic disks, and the slider assemblies may be positioned at one or both of the opposite sides of each of the magnetic disks.
Each magnetic head slider assembly in magnetic disk drives of the type referred to is typically coupled to the free outer end of a different one of a plurality of elongated arms or load beams. The slider assembly is mounted in a manner to permit gimballed movement at a free outer end of the arm so that an air bearing between the slider assembly and the surface of the rigid magnetic disk can be established and maintained. The elongated arm is coupled to an appropriate mechanism for moving the arm across the surface of the disk so that a magnetic head contained within the slider assembly can address different ones of concentric data tracks on the disk for writing information into or reading information from the data tracks.
An example of an arm assembly having a gimballed mount for a magnetic head slider assembly is provided by U.S. Pat. No. 3,931,641 of Watrous. The arm assembly described in the Watrous patent includes a relatively rigid load beam having a rigid bearing member at a free outer end thereof for receiving a protuberance on a spring element. The spring element is spot welded to the load beam and has an end thereof defining a flexure. The flexure includes a pair of stiff crosslegs mounted on an opposite pair of flexible outer fingers and a central finger. The central finger mounts a magnetic head slider assembly, and gimballed movement is provided by the load protuberance on the spring element which is held in contact with the bearing member at the end of the rigid load beam. Such arrangement provides desired gimballing action by allowing a pitch and roll of the slider assembly around mutually orthogonal axes while at the same time resisting radial, circumferential and yaw motions.
In magnetic disk drives of the type described, physical contact of the surface of the magnetic disk containing the data tracks by the slider assembly must be avoided. Consequently arrangements must be provided for preventing such contact when the magnetic disk is at rest or is otherwise not rotating at its nominal operating speed. When the disk is rotating at its nominal operating speed, the air bearing between the slider assembly and the disk is usually sufficient to prevent contact therebetween. One technique commonly employed is to move the slider assembly onto a portion of the disk where physical contact can be tolerated whenever the disk is decelerated to rest. One or more so-called parking zones are provided on the surface of the disk where the slider assembly may rest. When the disk is accelerated to its nominal operating speed, the air bearing again forms and the slider assembly may then be moved to the data tracks. Another common technique for preventing contact between the slider assembly and the disk surface when the disk is decelerated to rest is to pivot the arm so as to move the slider assembly away from the surface of the disk. This moves the slider assembly into an unloaded position well away from the disk surface. When the disk is again accelerated to the nominal operating speed, the arm is pivoted so as to bring the slider assembly back into a loaded position in which the air bearing forms between the slider assembly and the surface of the disk.
An example of an arrangement for raising and lowering the arm so as to move the slider assembly between loaded and unloaded positions is provided by a copending application of Warrent L. Dalziel, Ser. No. 759,900, filed July 29, 1985 and commonly assigned with the present application. The Dalziel application describes a mechanism for loading and unloading one or more slider assemblies using simple mechanical apparatus. Such apparatus engages the arms to raise them into unloaded positions and at the same time limit their radial movement. A separator element is movable between first and second positions to selectively engage the arms. When the separator element is in a first position, the slider assemblies are in loaded positions, and radial motion of the slider assemblies is not inhibited. Movement of the separator element into a second position moves the slider assemblies into unloaded positions and at the same time locks an associated carriage assembly in a selected position to inhibit radial motion of the slider assemblies.
Each time the disks are decelerated to rest in the arrangement described in Dalziel application Ser. No. 759,900, the slider assemblies are raised into the unloaded positions and at the same time radial movement of the arms is limited. This does much to protect the sensitive components of the magnetic disk drive against damage due to shock loads such as may occur if the disk drive is dropped or otherwise bumped. Nevertheless, depending upon the manner of coupling the slider assemblies to the ends of the elongated arms, it may be difficult or impossible to prevent damaging contact between the slider assemblies and the disk surfaces. This is so even though the arms are pivoted to move the slider assemblies into unloaded positions well away from the disk surfaces. Inadvertent dropping of the magnetic disk driven onto a hard surface or other application of severe shock loads may still result in the slider assemblies contacting the disk surfaces with possible damage to the slider assemblies or the disk surfaces or both. Typically the slider assembly is coupled to the free outer end of the arm by a flexure element which is highly flexible and which therefore permits substantial movement of the slider assembly away from the arm in response to shock loads and other substantial forces.
Accordingly, it is an object of the invention to provide an improved magnetic disk drive, and particularly an improved disk drive of the type in which one or more magnetic head slider assemblies are employed in conjunction with one or more rigid magnetic disks.
It is a further and more specific object of the invention to provide an improved magnetic disk drive in which the possibility of damaging contact of the disk surfaces by the slider assemblies in response to shock loads when the arm is raised into an unloaded position is greatly minimized or eliminated.