Abstract: The mixed potential of a standard reference electrode and an electrically conductive article that is being electrolessly plated is compared to a DC reference voltage. A predetermined level of comparison indicates the start of electroless plating. This comparison starts a timer. After a predetermined time interval has expired, plating is terminated. The result is a plated coating that is uniform and of a closely controlled thickness. The article to be plated is a thin film magnetic recording disk upon which a thin cobalt containing layer, in the range of about 850 angstroms thick, is to be plated.

Abstract: A magnetic disk drive channel circuitry is shown and described that generates eight incremental values of write current and eight incremental values of delta-V (the minimum voltage change per unit time which tests signals to discriminate between data and noise). Each of these variable parameter values may be program selected by a three bit bus signal. This variability testing of an adaptation to the optimum parameter value for each head media combination and by grouping tracks in contiguous data bands, the parameters may be optimized for tracks near the inner diameter, the outer diameter and in the middle band. The variable delta-V can also be used as an additional data recovery tool wherein re-reading with a lower value enhances recovery of missing bit errors and re-reading with an increased value can assist recovery from an extra bit error.

Abstract: A disk file of the kind employing a vented hub assembly and slotted spacers between disks to provide a passage for circulatory airflow employs a filter assembly extending circumferentially around the axial region of the hub assembly. The primary path for airflow is from a high pressure region at the periphery of the disks, through the filter assembly into the vented hub assembly and out again via the slotted spacers. A parallel leakage path between the filter itself and the hub assembly is limited by making the separation between a substantially planar surface of the filter assembly and the adjacent disk uniform and very small. Airflow rates through the filter are consequently enhanced.

Abstract: In a magnetic disk file having a plurality of disks and a source of organic lubricant mounted within a housing, an air flow stream recirculates within the housing. The vapor pressure of the lubricant source is controlled to provide vapor phase transport of lubricant molecules between the source and the disks' recording surfaces. The lubricant molecules bidirectionally transfer between the air stream and the source, and between the air stream and the surface of the disks, as is needed to maintain a mono-molecular lubricant film, in the range of about 3 to 15 angstroms, on the disks in accordance with the principle of Langmuir kinetics. The disks are rigid disks and their recording surface includes a carbon overcoat. This overcoat has an affinity for the airborne organic lubricant molecules.In a first embodiment, the vapor pressure of the lubricant is controlled by mounting the material at the coolest location within the housing.

Abstract: A power switching circuit for switching power repetitively to a load at a relatively low frequency employs a power switching device which is driven across an isolating transformer interface. The drive signals are high frequency pulse signals which are modulated with the low frequency switching information, the modulations being detected in the secondary circuit of the transformer. Such an arrangement affords isolated driving with fast switching edges and requires only a small transformer. Power for the detection circuit is derived by rectification of the high frequency signals induced in the transformer secondary.

Abstract: Method for measuring the properties of a slider/disk interface in a magnetic disk storage apparatus by measuring a triboelectric current flowing between disk and slider. Rotational speed is adjusted between 100 and 500 rpm so as to obtain a frictional contact between disk and slider. The shape of the tribo current curve obtained during the measuring time interval is analyzed. An early maximum of the tribo current amplitude and a subsequent continual decay indicates a good slider/disk interface and a long lifetime.

Abstract: The circuit provides damping for digitally controlled devices where the provision of power pulses in response to sensing a given device parameter may result in a regularity of pulses that causes a resonant condition with a frequency that interferes with other device functions or induces error conditions. The circuit shown randomizes to a motor by random gating of a sequence of commands retained in a shift register. Random gating from the shift register positions occurs through the use of a counter driven by an oscillator, independent of other device functions and clocking circuits, in conjunction with an enabling circuit from a random digitized data source that enables or disables counter advance by the oscillator.

Abstract: An enclosure for a rigid disk data file is shown which includes a base casting and a cover that interface along planar surface that is not perpendicular to the axis of the spindle supporting the data disks. The base casting at one side extends axially along the disk stack and has the transducer positioning actuators mounted through openings therein. At the opposite side, the disk stack is fully exposed to permit easy access to the disk surface for procedures such as servo writing during manufacture of the drive. This structure makes possible concurrent operation of the product heads and servo writing heads.

Abstract: An actuator for positioning transducers with respect to a disk storage device data surface provides a substantially sealed head-disk enclosure from which the voice coil motor permanent magnets are excluded. The mounting flange-inner core member, end cap and collar and shorted turn provide a sealed enclosure about the transducer carriage, voice coil and working air gap of the voice coil motor (VCM) with the permanent magnet and outer core pieces assembled to the device thereafter. The permanent magnets can be excluded from the clean room assembly area and this source of the most destructive particulate contamination are outside the head-disk enclosure.

Abstract: A controller for a voice coil motor driven disk file actuator is described. The device has an online adjustable gain characteristic for controlling movement of the actuator assembly and an estimator that estimates actuator velocity and bias. Forward gain is estimated from position and coil current measurements and compared with a nominal value to create an error signal used to adjust the controller and estimator gain characteristics. The control technique allows changes in the open loop system without changing the closed loop performance. By monitoring loop gain it is possible to alter compensator gains to maintain a constant closed loop performance.

Abstract: A velocity estimator for a voice coil motor driven actuator is implemented by integrating coil current to generate the estimated velocity and integrating the estimated velocity signal to produce an estimated position signal. The estimated position signal and a measured position signal are compared and the derived error signal is applied as negative feedback to the summing junctions at the inputs of each of the integrators. The use of an integrated signal results in reduced noise influence on the position error signal which, in the environment of a data disk drive, results in more reliable recording of track crossings and the ability to meet rigid product specifications using simple servo patterns.

Abstract: A magnetic head actuator assembly for a disk drive, having dissimilar materials with different linear expansion coefficients, is provided with thermal compensation. The movable member of the actuator assembly has spring elements attached at spaced locations thereon and is associated with a cooperating pulley that drives a band. The band ends are connected to the spring elements such that rotation of the pulley imparts motion to the movable member. The spring coefficient of the band, spring, and connector structure between the pulley and one spaced location and the spring coefficient of the band, spring, and connecting structure between the pulley and the other of the spaced locations on the movable member are chosen so that the displacement of the magnetic head with respect to a record track on a cooperating disk surface caused by temperature variation is compensated. In one modification, a bimetal is used to replace a spring element in the thermal compensating system.

Abstract: A voice coil motor for a moving storage media actuator has a permanent magnet assembly wherein a radially polarized magnet is formed as sectors, with like sectors of the outer housing which forms a portion of the pole piece assembly. These sectors are then mounted on the remainder of the pole piece assembly for the magnetic actuator to form a cylindrical magnet and cylindrical outer pole piece. The sectors require no further attachment or adhesive in addition to the magnetic field and provides substantially zero clearance contact between magnet and pole piece, to afford a continuous magnetic path interrupted only by the working gap through which the voice coil travels.

Abstract: A disk file control provides for tracks having defective sectors by forming sectors as a single, uninterrupted stream of serial data containing both identifier (ID) and data portions. Reading a single ID portion characterizes the entire track to permit writing data without a separate revolution to read the ID field. The ID information includes the offset of the first logical sector on the track and the locations of defective sectors that must be skipped. As soon as one ID is read, the location of the addressed sector is ascertained and the ID data for the sector to be written is formulated so that the entire sector including both ID and data can be written when the sector first approaches the transducer. If alternate sectors are permitted on a subsequent track under the strategy being used, a single ID on the track will define where the logical sectors making up that track will appear (either the physical sector location on the track or at an alternate location on the next track).

Abstract: A disk file data disk stack assembly is clamped using a preloaded heat shrink ring that has an interference fit with the assembly hub. In addition to an inner diameter slightly smaller than the cooperating hub surface, the shrink ring has a full or extended outer cylindrical surface and a reduced area inner cylindrical surface and a reduced area axial end surface to permit effective heat transfer to the ring with minimal conductive heat transfer to the hub and clamping element to enable a differential temperature for effecting shrink ring removal when required.

Abstract: A glide head is used to test a rigid magnetic disk surface for projecting asperities. Using a two rail head with the read/write transducer mounted at the rear of the rail at the side of the head toward which the head is being radially advanced and skewing the head so that the trailing edge of the head approaches each track before the leading edge as the head is advanced, it is possible to write a pattern from a known position relative an event or asperity identified by a mechanical transducer associated with the head to the index location. Using a developer, it is then possible to readily identify the asperity during microscopic examination of the disk surface.

Abstract: A cartridge filter for an enclosed magnetic disk drive is disclosed which includes a dual media drum type filter element in a recirculating filter assembly that surrounds the breather filter and delivers air from the periphery of the disk stack to the axial entry of the ventilated disk spindle assembly. The cartridge provides an extended media surface within a compact space for frequent cycling of the enclosed air volume through the filter.

Abstract: An optical tool is disclosed which permits a sequence of aligned transducer gaps to be positioned parallel to the axis of a disk file. The tool is surfaced with transparent material, has a thickness the same as the disk or disks of a disk stack being simulated and presents an etched alignment grid at the interface surface between transducer and tool. The virtually common plane of the transducer gap and etched grid substantially eliminates parallax and the unfilled etched grid permits the gap to be seen, whether aligned with the transparent unetched surface or the translucent etched surface portion. The use of inclined mirrored surfaces underlying the grid permits alignment to be effected using a bright field microscope and observing from a direction rotated 90 degrees from a line perpendicular to the grid to enable alignment of transducer gaps confronting one another at opposite sides of the disk.

Abstract: An improved method and formulation is shown for preparing polishing media for superfinishing pure metal surfaces. A combination of hydrophobic and hydrophilic silicone surfactants is used to control the porosity and water absorption during use whereby durability is obtained and the catalyst concentration is regulated to control hardness to achieve durability without scratching the workpiece. Density is controlled by the quantity of mixture with which a closed mold is charged. To produce successful media it is also necessary to preheat the closed mold and to be certain that the resin mixture of particles, polyol and additives does not exceed 120 degrees F. prior to final mixture with isocyanate just before charging the mold and curing. Also a longer cure at a lower temperature enhances the qualities of the resulting polishing media.

Abstract: A rigid magnetic storage media coating composition using a high concentration of magnetic particles includes a dual thermoset binder system. The two polymers forming the dual binder system cure during mutually exclusive temperature ranges to form polymer networks that are interpenetrated and entangled. The thermoset polyurethane-melamine/polyester polymer binder system possesses improved properties including the ability to retain liquid fluorinated polyether lubricant without spin-off. The addition of a small amount of silicone wax to the uncured coating composition enhances composition rheology during spin coating on a rigid substrate.