Abstract: A pipeline pig assembly having an improved pig implement and retaining apparatus for retaining the pig implement, the improved retaining apparatus comprising a body extension member connectable to the body portion of the pipeline pig to support at least one pig implement. The pig implement is securely retained on the body extension member by a retaining collar fastened on the body extension member, and the pig implement has a pattern of recesses which are interlockable with retaining collar bosses or with bosses of a spacer member when multiple pig implements are supported.

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: 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 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: An expanding gate valve assembly comprising a gate, a stem for actuating the gate and floating segments movably mounted on opposite sides of the gate for movement relative to valve seats on a valve body. The valve seats on the valve body are inclined to the axis of the stem, and the segments are provided with correspondingly matching inclined surfaces. Movement of the segments is arrested by stops on the valve body, thereby making the segments expand laterally during closure The gate has a lower gate part having a through conduit which is alignable with a fluid flow passageway in the valve body in the open position, such lower gate part having tapered surfaces parallel to the incline of the valve seats to seal therewith and establish fluid tight communication between the through conduit of the gate and the fluid flow passageway.

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: An improved prefeeder assembly for shingling sheets of planar material in which a sheet stack is positioned on a prefeeder lift conveyor which lowers the sheet stack into a floor pit to incrementally elevate the sheet stack. A block pusher assembly sequentially pushes block segments to a conveyor assembly where a shingling assembly shingles the sheets. A bottom sheet removal assembly having an in-path diverter plate contacts and diverts only the bottom sheet of the bottom most block segment as this block segment is being shingled. As shingled sheets are discharged to other process equipment, a tamping assembly actuated by balloon cylinders serve to tamp the sheet edges for uniform restacking.

Abstract: An expanding gate valve assembly which includes a gate, a stem for actuating the gate, a segment mounted on one side of the gate, or in an alternate, bidirectional embodiment, two segments with one segment movably mounted on each opposite side of the gate for movement toward seating surfaces within the valve body. Each segment carries two spaced, parallel wedging-camming surfaces which are of a configuration to cooperate with complementary spaced, parallel wedging-camming surfaces on the gate to effect lateral expansion of the segment or segments during closure or opening of the valve. The spacing of the wedging-camming surfaces or legs is such that the movable segments are stably supported during their expansion movement.

Abstract: An improved sealing is provided for repairing a breach of down hole casing integrity, while maintaining substantially unrestricted annular fluid communication through the length of the well bore which comprises a casing sleeve supported on a tubing string for providing an alternate liquid or gas flow route about the tubing string at the defective portion of the casing. The casing sleeve is disposed between and connected to a first and second seal support housing assembly, each of which has an internal bore and a retaining end portion dimensioned to prevent a tubing collar of the tubing string from passing therethrough. Resilient casing engaging members are supported on each of the first and second seal support housing assemblies such that the resilient casing engaging members provide an effective seal between the first and second seal support housing assemblies and an adjacently disposed internal wall of the casing.

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 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..