Abstract: A circular disc drive disc clamp having a plurality of oval-shaped screw holes. The oval shape prevents the interference of the outer edge of the clamp's mounting screws. This permits the use of larger mounting screws to provide increased shock resistance. It also moves the screw contact inward to smooth the spring rate of the clamp around its periphery. It also reduces the overall stack height of the clamp and spring combination.

Abstract: A data transfer circuit for coordinating transfer of data between a host and a disc of a disc drive having a state machine for coordinating with a buffer controller to transfer data between the host and a buffer segment and a second state machine for coordinating with the buffer controller to transfer data between the buffer segment and a disc of the disc drive. Counting circuits count the number of bytes transferred between the host and the buffer segment and between the buffer segment and the disc and provide sector count signals each time a sector of data is transferred into or out of the buffer segment. The sector count signals are received by a buffer manager which includes counters for counting sectors of data transferred into and out of the buffer segment and a comparator circuit that compares the contents of the buffer manager counters to provide a code indicative of the state of the buffer segment to a decoder.

Abstract: Apparatus for supporting transducer heads of a hard disk drive wherein the heads are mounted on transducer support arms that are, in turn, mounted on extensive fingers formed on an actuator that moves the heads across surfaces of data storage disks. Two holes are formed through each finger to form two coaxial sets of holes on the actuator body and one hole in each finger receives a tubular boss formed about one of two equally spaced holes formed through one end of each support arm each arm. Bosses inserted into coaxial holes in the fingers extend thereinto from the same direction and are swaged to fix the support arms to the actuator by passing a ball through the bosses from the opposite direction. The support arms are constructed by spot welding swage plates, each having two holes formed therethrough and having a boss about one hole, to leaf members, similarly having two holes formed therethrough, whereon the transducer heads are mounted.

Abstract: A limit stop for defining the extremes of the range of motion of a disc drive actuator, and a magnetic latch which may be incorporated into the limit stop for holding the actuator at one of the extremes of its range of motion. Both the limit stop and limit stop with incorporated magnetic latch allow compliance to be determined based on material selection and dimensions. The magnetic latch includes a flux concentrator mounted on a limit stop and a magnetically permeable striker mounted on the moving portion of the actuator, and derives magnetic force for latching from the permanent magnet in the voice coil motor of the actuator.

Abstract: A hard disc drive having a digital servo system for controlling the position of a servo head on a dedicated servo surface. The servo surface is formatted in a series of consecutive frames along concentric tracks, each frame passing the servo head in a time that defines a sampling interval for the servo system. The frames contain track address and position fields for locating the servo head and location can be effected in relation to limited or extended fine control regions about the tracks via signals transmitted to a position circuit utilized to generate a servo position error from the position field. The position circuit generates a track phase code for checking track addresses generated by a track address circuit used to generate a track address from the address field.

Abstract: The present invention is directed to the structure of the permanent pole pieces, the permanent magnets and the bobbin of a voice coil motor. The poles, poles and permanent magnet(s) or poles, permanent magnets or any combination thereof are shaped in such a manner as to provide as large and constant magnetic flux field strength over a given area. The shaping of the components of the voice coil motor results in an altered external geometrical shape of the voice coil motor envelope, a reduced envelope for a motor of a given torque capability or both. The shaping of the poles, permanent magnets or bobbin allows the voice coil motor to consume less room within the disk drive housing.

Abstract: A data storage system comprised of a plurality of disc drives which each comprise a plurality of data storage discs rotated by a polyphase motor. Each disc drive has a servo system for radially positioning transducer heads proximate the disc surfaces and generating an index signal for a selected orientation of the discs. A reference signal generator in each disc drive produces a reference signal at each of a succession of time intervals equal to the desired period of rotation of the discs and the disc drives are interconnected to enable each disc drive to sense a reference signal generated by any other disc drive. Each disc drive includes a microcomputer that is periodically interrupted and, during the interrupt, transmits the reference signal generated by the disc drive to the other disc drives in the absence of reception of a reference signal from another disc drive prior to the interrupt to provide a common reference signal for all of the disc drives.

Abstract: A prewrite compensation circuit for use with a hard disk drive wherein surfaces of disks of the drive are formatted for writing data to the surfaces at different frequencies selected for different concentric zones on the surface. Data to be written is passed through a shift register to a series of delay elements and a multiplexer that passes the output of a delay element selected in relation to a data word received by the multiplexer to a write circuit that writes the data to the disc. The delay words, or elements of delay words, are stored in latches that are selectively connected to the multiplexer, or a delay word accumulator connected to the multiplexer, in relation to the pattern of bits surrounding a bit to be written.

Abstract: A circuit for enabling the writing of servo data by a servo transducer to a dedicated servo surface of a hard disk drive during the manufacture of the drive while enabling only the reading of servo data at subsequent times that the drive is mated to a computer. The circuit receives power on selected terminals of a connector and includes a level detector that provides a first control signal in response to a power supply voltage level that is below a level selected to exceed voltage levels available from the power supply of a user computer and a second control signal in response to a power supply voltage above the selected level. The second control signal is transmitted to a switch assembly that responds by providing a direct connection between the servo transducer and data terminals of the connector. The first control signal is transmitted to switches by means of which an amplifier, having inputs connected to the transducer and outputs connected to the data terminals, is supplied with electrical power.

Abstract: A shock load detection device mounted on a disk drive unit. The detection device is comprised of a piezoelectric polymer film encapsulated and electrically shielded by a metallic or metallic coated package. Electrical contacts are provided for on the piezoelectric polymer film and are connected to amplification and comparator circuitry which issues a write fault signal upon detection of external force in excess of a predetermined threshold. The shock sensor may be mounted on the computer disk drive of the unit in such a manner as to be at a 45.degree. angle to each of the x, y and z axis of the orthogonal coordinate system so that linear and torsional forces may be monitored.

Abstract: A method for correcting track counting errors during seeks of a servo head across the surface of a rotating disc of a hard disc drive. The number of tracks remaining in the seek is maintained in a tracks-to-go counter and the value in the counter is stored along with a plurality of previously stored counter values during each a sequence of equal time intervals. Potential track counting errors are detected by applying a first criterion to the stored counter values and first criterion is selected to yield false error detections for patterns of stored values satisfying a second criterion. For each potential track counting error, the second criterion is applied to the stored counter values and the tracks-to-go counter is incremented a selected number of times for patterns of stored values that do not satisfy the second criterion.

Abstract: A self-holding latch assembly for a disc drive storage device to alternately lock or unlock the actuator of the disc drive storage device, the latch assembly including a magnet coil means supported in a predetermined spatial relationship to the actuator for alternately providing magnetic attraction to a first limit stop or to a second limit stop in response to current flow therethrough. A magnet latch assembly is pivotally supported by the magnet coil means and is alternately attracted to the first limit stop or to the second limit stop, the magnet latch assembly having engagement with the actuator for locking same in one such position, and being in clearing relationship to the actuator in the other stable position.

Abstract: A hard disk drive having a plurality of disks mounted on the rotor of a current limited, electronically commutated dc motor. Windings on the stator of the motor are divided into serially connected run and start sections and first and seconds drive circuits are provided to operate the motor by alternatively enabling the first drive circuit to pass currents serially through the two sections of the winding and enabling the second drive circuit to pass currents through only the run sections of the windings. During spin up of the disk drive to operating speed, the first drive circuit is enabled and the second drive circuit is disabled to drive the disks to the speed at which the back emf limits on the acceleration of the motor using both sections of the windings reduces the acceleration to the maximum acceleration achievable at the current limit using the run sections alone. Spin up is then completed by enabling the second drive circuit and disabling the first drive circuit.

Abstract: An acoustically damped disc drive assembly having a housing, the disc drive assembly having internally disposed components capable of generating acoustic vibrations, the housing having a cover comprised of a plurality of plate members, each pair of the plate members having a damping layer disposed therebetween for damping acoustic vibrations imparted to the cover by the internally disposed components. In addition to the damping layer, which is preferably a viscoelastic material compositely bonding such plate members together, an acoustic isolator area may be provided to surround the attachment points of the internally disposed components to the cover in order to provide further damping of the acoustic vibrations.

Abstract: A disk drive assembly includes a disk pack with an axially retractable spindle assembly, along with a rotary actuator, mounted within a unitary deck and precision aligned by bores through spaced apart upper and lower support walls of the deck. Bushings, mounted to opposite ends of a spindle shaft through bearings, are aligned with the bores by inserting the retracted spindle assembly into the deck, with a spring biasing the spindle assembly into the retracted position. Fasteners through the opposed support walls draw the bushing sleeves axially outward against the spring force to preload the bearings as the shaft is aligned and secured, without employing a jig or any other alignment tooling.

Abstract: A method for optimizing settle characteristics of a read/write head on a data track on a rotating disk of a hard disk drive following a seek to the data track wherein each data track is assigned to a selected on of a plurality of concentric zones defined on the surface of the disk. Seeks are performed by a servo system in relation to a compensated velocity demand profile that provides velocities the head is to have at selected distances from a destination track and is selected for each zone by adding a velocity increment specific to the zone to a stored velocity demand profile for movement of the head in one direction and subtracted from the stored velocity demand profile for movement in the opposite direction.

Abstract: A method for effecting a transition from data track following by one data head adjacent one disk of a rotating disk data storage device to data track following by a second data head adjacent a second disk wherein the data tracks are part of a cylinder of tracks including a servo track followed by a servo head with an offset appropriate to each data track. A servo control circuit between the servo head and the coil of an actuator on which the heads are mounted receives a position error signal from the servo head and an offset signal from a microcomputer during following of each track and the transition is effected by adjusting the offset signal in a succession of discrete steps from the offset appropriate for one data head to the offset appropriate to the other data. Steps of the succession can have magnitudes equal to successively selected proportions of the offset signal difference for the two data heads or can vary alternatively between the offset signal difference for the two heads and a zero magnitude.

Abstract: A method of writing servo patterns to the surface of a disc of a hard disc drive without magnetizing the transducer head by means of which the patterns are written. The surface is initially magnetized in one direction through the transducer head while the disc is rotating to move the disc surface by the transducer head. Each servo pattern is subsequently written by passing a current through the transducer in the opposite direction for selected time interval. Following writing of each pattern, a current is passed through the transducer head in the direction used to initially magnetize the disc for a time interval equal to the time interval during which the pattern was written.

Abstract: A magnetic thin film recording medium is provided for longitudinal recording of magnetic flux transitions, with the read-back signals enhanced due to a substantial reduction in media noise. The reduced noise level is the result of a unique vacuum deposition process for applying an underlayer to a substrate, prior to deposition of the magnetic thin film. In particular, the underlayer is deposited in a low temperature plasma process under increased pressure of argon or another inert gas and at reduced deposition rates, thus to create voids or interstitial areas which substantially isolate individual grains from their neighboring grains. The subsequently deposited magnetic thin film replicates the crystalline structure and orientation of the chromium underlayer, for relatively isolated grains in the recording layer. This results in lower media noise levels, approaching or equalling those characteristic of particulate media.

Abstract: .[.A vent cap has.]. .Iadd.A low diffusion disk drive breather vent for communicating air between the interior and the exterior of a sealed disk drive housing through a vent passageway, .Iaddend.a long, narrow air communication passage .[.covering the vent outlet of a sealed disk drive. The passage reduces.]. .Iadd.provided to reduce .Iaddend.diffusion of water vapor .[.into the disk drive.]. .Iadd.through the passage.Iaddend..