Abstract: A disc assembly for a disc drive has a balancing clip mounted on a shoulder formed on other portions of the assembly to balance the disc assembly. The disc assembly includes a cylindrical hub on which data storage discs, interspersed with ring shaped spacers, are mounted and the discs and rings are clamped into place on the hub between a flange formed on one end of the hub and a clamp ring that is secured about the other end of the hub by heat shrinking the clamp ring onto the hub. A circular shoulder is formed coaxially with the hub on a face that is, in turn, formed perpendicularly to the hub axis on either the clamp ring or the end of the hub adjacent the clamp ring. The balancing clip is a C-shaped lamella having a circularly arcuate inner periphery for mating with the shoulder. The outer periphery of the balancing clip is elliptically arcuate and is bilaterally symmetric with respect to the major axis of the ellipse to which the outer edge conforms.

Abstract: A method for effecting seeks of a transducer head across a data storage disk wherein the head is accelerated over a first sequence of time intervals and decelerated over a second sequence of time intervals. In each time interval of the first sequence, the head is accelerated in relation to the difference between the actual head velocity and a current demand velocity that is determined by incrementing the demand velocity for the previous interval by an amount that is a fraction of the difference between the previous demand velocity and a stored profile velocity selected in accordance with the current location of the head. In each time interval of the second sequence, the head is decelerated in relation to the difference between the actual head velocity and a stored profile velocity selected in accordance with the current location of the head.

Abstract: Method and apparatus for controlling the timing of the sampling of signals and signal amplitude in a PRML read channel. A VCO generates a read clock and a clock generator connected to the VCO generates even and odd clock signals corresponding to even and odd cycles of operation of the VCO. Serially connected even sample and hold circuits respond to clock signals to store samples of the read channel signal taken during successive odd cycles and serially connected odd sample and hold circuits store samples taken during successive even cycles. Comparator circuits compare the samples taken in each cycle to reference signals and the comparisons are clocked through two stage, even and odd shift registers to provide estimates of the presence or absence of nonzero samples for each even and odd cycle.

Abstract: A maximum likelihood detector for a disc drive in which data files are stored along tracks as a sequence of magnetically written data elements that give rise to a signal in the disc drive read chapel. The detector includes even and odd Viterbi decoders that determine the most likely even and odd subsequences of data elements from even and odd samples of the signal and a postcoder that generates the most likely sequence of bits of encoded user data from the subsequences.

Abstract: A method for following data tracks on data surfaces of a disc drive by organizing the data tracks in concentric cylinders including servo tracks on a dedicated servo surface and following servo tracks with a servo transducer that is offset from the servo track to align selected data transducers with the data tracks. To measure the offset for each data surface, a calibration correction track is written to one data surface while a track on the servo surface is followed and the correction track is read by a thermal calibration circuit while following the servo track with an offset to obtain a calibration correction indicative of electronic offsets in the thermal calibration circuit.

Abstract: A control system is provided for an ion implanter having an electron shower filament and a Faraday flag provided wherein the electron shower output is adjusted to maintain substantially continuous control of disk current during implantation, the control of the disk current of a target wafer during implantation being achieved by electrically isolating the target wafer, monitoring the disk current, and maintaining the electron shower filament current of the ion implanter at a level which permits rapid adjustment of the disk current during the time period required to close the Faraday flag.

Abstract: A brake pulsing apparatus for use in vehicles having vacuum hydraulic, pneumatic or electric brake systems. The brake pulsing apparatus includes a solenoid valve, for vacuum hydraulic and pneumatic brake systems, or a relay, for electric brake systems, mounted in a vacuum, pressurized air or electrical line that transmits a brake signal to a brake assembly of the vehicle when the brake system is engaged, a pendulum and proximity switch that sense deceleration of the vehicle, and a timer relay connected between the proximity switch and the solenoid valve or relay to repetitively close the valve or open contacts of the relay when the brake system is engaged. The pendulum and timer relay are adjustable to adapt the brake pulsing apparatus to the type of vehicle in which the apparatus is used.

Abstract: An educational and entertainment device wherein a microcomputer is mounted in a housing to receive user generated data presented by moving a conducting stylus across perpendicular arrays of conductors on a work surface formed on the housing and presents information to the user via audio and visual devices. The conductors of each array are organized into first write groups formed of a plurality of interconnected conductors which can be placed in a selected electrical state by words written to the write groups and into read groups, read by the microcomputer, formed of a plurality of interconnected conductors interspersed with the conductors of the write groups. Additional, second write groups are interspersed with the first write groups and read groups. The arrays are alternatively mounted on the work surface or on a support member which can be detachably mounted on the work surface and connectors are provided for connecting the arrays on the support member to the microcomputer.

Abstract: A pivot mechanism for a rotary actuator in a disc drive data storage device comprising a pivot shaft having a shoulder near one end thereof, the pivot shaft disposed in a central bore of an actuator body having a medially disposed narrow section spatially separating upper and lower bearing assemblies supported on the pivot shaft. Tolerance rings are disposed between the bearing assemblies and the actuator body, and a preloading resilient member biases the bearing assemblies to abut against the narrow section and the shoulder on the pivot shaft. Preferably, adhesive bonds the upper bearing assembly to the pivot shaft once preloading is achieved.

Abstract: A method for compensating for position and component induced variations in the acceleration and deceleration capabilities of a voice coil actuator in a disc drive, comprising the steps of dividing the discs radially into a plurality of zones, testing the acceleration and deceleration capability of the disc drive in each zone by performing specially controlled seeks in both inward and outward directions in each zone, comparing the result of these specially controlled seeks with a calculated nominal or desired result, and calculating a compensation factor for each zone which is applied by the servo system to all subsequent seek and track following operations.

Abstract: An air cleaner assembly for capturing and filtering fumes is provided which comprises a housing having an inlet and an outlet, a pair of filter cartridges supported therein and a blower. A channel and baffle assembly direct the flow of air drawn into the housing in a vortical pattern around the filter cartridges to separate heavier particles in the air and to efficiently draw the air through the filter cartridges. The separated particles collect in a pair of dust trays that are provided with flow directional lips to prevent the vortical air flow from disturbing the deposited particles. A backflushing assembly cleans the filter cartridges of the particles that are collected thereon by pulsing the particles away with a blast of air directed through the entire length of the filter cartridges.

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 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: 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 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 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 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.