Abstract: A shock load detection device mounted on a disk drive housing of a computer disk drive unit to issue a write-fault signal should the disk drive unit have a mechanical shock imposed thereon. The detection device includes three piezo-electric crystals mounted orthogonally between a base and a seismic mass. Any shock load along x, y, and z axes through the piezo-electric crystals produces an electrical charge which is amplified, filtered, and compared for issuing a write-fault signal. The write-fault signal is used to stop the writing of read/write heads on a spindle of a head disk assembly before the shock imposed thereon could otherwise move the read/write heads off track causing a data error.

Abstract: An apparatus for testing the surface properties of a material is disclosed. The apparatus includes an indentor which is suspended above the surface of a sample and dropped onto the sample. Several testing methods are also disclosed. Surface toughness is measured by dropping the indentor from a variable height and inspecting the surface for failure. Thin film strength is tested by making several drops from various heights and inspecting the surface for flaking of the layer. In addition, damping capacity can be measured by comparing the kinetic energy of the resulting from the drop of the indentor to the strain energy measured by a probe on the opposing surface of the sample.

Abstract: A magnetic disk memory data storage device has a unitary arm assembly mounted for rotation by an actuator for carrying the tranducers and shifting them across the disk surfaces. The assembly is subjected to varying temperature during normal operation of the device which causes differential rotation of the individual arms and consequent misalignment of them. In a design of interest, the arm nearest the deck is most affected. At least some of this misalignment can be compensated for by placing a slot in the edge of at least one arm and placing a body with a different thermal coefficient into the slot with an interference fit. If the body has a smaller thermal coefficient than the arm assembly's, the slot should be on the edge opposite the direction in which the misalignment occurs.

Abstract: A suspension is provided for supporting a magnetic transducing head with respect to a carriage, for movement with the carriage and relative to a substantially planar magnetic recording surface. Two parallel and spaced apart flexure arms extend from the carriage, and are extremely thin in the dimension perpendicular to the recording surface. The remote ends of the flexure arms are joined by an elongate rigid cross-bar directed transversely of the arms. The transducing head is fixed to the cross-bar, intermediate the flexure arms. When the recording surface is moved, an air bearing between the recording surface and head stabilizes the head, and the flexure arms are constrained to behave as elastic beams fixed at both ends. In particular, the flexure arms are subject to lengthwise torsional bending, and pure bending about axes parallel to the cross-bar, enabling the head/cross-bar assembly to respond in gimbal fashion to recording surface irregularities.

Abstract: A single magnetoresistive element ganged MR head sensor. The sensor is comprised of a single magnetoresistive element divided into a plurality of sense regions by more than two electrical contacts, the facing sides of each being parallel to each other and perpendicular to the lower edge of the element. No other transverse biasing is applied and the sensor operates in a non linear mode. The provision of no transverse biasing reduces cross talk.

Abstract: A metastable prevent circuit comprises a plurality of parallel channels, each coupled to receive and synchronize asynchronous pulses to a synchronous clock signal. A shift register is responsive to the asynchronous pulses to sequentially enable individual ones of the channels. In the case of a two-channel system, the shift register is a bistable device which enables the channels alternately.

Abstract: A wiper guide assembly, mounted at the free end of a workpiece carrying arm, can be selectively released to position a neoprene wiper blade against a lapping surface, and retracted whereby the blade is lifted away from the lapping surface. The wiper blade is located just ahead of a workpiece supported by the arm, and between the workpiece and a source of abrasive slurry supplied to the lapping surface. When retracted, the wiper blade is spaced apart from the lapping surface to expose its associated workpiece to the abrasive slurry, permitting more rapid removal of material. When the assembly is released, the wiper blade contacts the lapping surface in a wiping engagement, to guide or divert slurry away from the workpiece, whereby the lapping surface contiguous with and about the workpiece is comparatively free of abrasive slurry.

Abstract: A lapping guide is provided to determine the position at which lapping of a thin film head to define pole faces should be terminated. Accurate positioning of the lapping guide with respect to the head is insured by forming various elements of the lapping guide during the same photolithographic process steps as those used to form elements of the head. The lapping guide may be used either as an electrical or optical guide. When used as an optical guide, a second lapping guide may be provided as an indicator that more frequency inspection is necessary.

Abstract: A thin film magnetic data transducer has for reading data a magnetoresistive sensing element with a projection not more than about 1.5 .mu.m. long under at least one of the poles. The projection's tip is approximately flush with the end of the pole, and because of its proximity to the medium, allows greater sensitivity in reading magnetic patterns in the recording medium. As long as the length of the projection is less than about the stated dimension (length measured normal to the medium surface) the sensing element does not break up into domains.

Abstract: A non linear magnetoresistive sensor having a magnetoresistive strip with no transverse biasing (either permanent or current) such that the sensor is operated in its non linear mode. The sensor is useful in its non linear mode to determine the location of pulse peaks from encoded data from a medium by differentiating and determining the zero crossings of the detected signal.

Abstract: A static electricity discharge device for a magnetic head formed by providing a recess to expose one of the conductors connected to the head's magnetic circuits. Static electricity buildup on the conductors discharges through the exposed portion of the conductor rather than through the pole pieces of the magnetic circuits.

Abstract: A process for fabricating magnetic transducing heads includes successive grinding, lapping and finishing steps. The ferrite cores of the transducing heads are rough cut with a silicone carbide grinding wheel, to an excess over desired final throat height equal to approximately one-half the nominal diameter of the grinding wheel grit. The core and supporting pads then are placed on a soft tin or lead rotating lapping plate for removing substantially all of the excess. Finally, the pads and cores are hand-finished on a stationary plate or soft tin, copper or lead. A diamond slurry used during lapping and final finishing, has a controlled alkaline pH in order to simultaneously chemically etch and polish the cores.

Abstract: This invention teaches a method for producing small machined parts by laser including a description of how to avoid sensitive edges of the work piece being machined and how to control beam size for maintaining uniform cavity depth over a relatively long work piece and also how to generate non-uniform cavity depth profiles on the surface of one or more parts. The invention also teaches that such a process can be used to produce satisfactory negative pressure air bearing sliders which are used to support the transducing magnetic heads for high density magnetic storage disk drives.

Abstract: This patent teaches multiplexing MR head circuits to an off-chip capacitor in novel ways to eliminate excessive numbers of off-chip components. The bias current is switched off for each MR head when it is not in use and the bias current is supplied only to the MR head being employed at a given time. On the sensing side, the invention teaches connecting a single capacitor across a plurality of pairs of transistor emitters, each pair of transistors having their collectors (assuming NPN) connected to the sense lines of one of the MR heads. A number of example circuits are illustrated and described, including one employing PNP transistors.

Abstract: A method and device for reading and recognizing an unknown character on a document, the device measuring the character's waveform amplitude along timed intervals and determining that each measurement is within a predetermined acceptable amplitude range at each interval for an ideal character. If all of the measurements of the amplitude are within the acceptable ranges, a recognition signal of the character is generated.

Abstract: A lapping plate is selectively textured for improved useful life and greater abrading consistency. Glass beads are serially propelled onto a lapping surface of the lapping plate in order to form spherical cavities of generally uniform size and distribution, and of a desired density. The cavities provide discontinuity in the lapping surface which substantially prevents workpiece hydroplaning. The cavities also receive loose abrading grit, workpiece fragments and other contaminants, resulting in more smoothly machined workpiece surfaces. Use of the lap plate with cavities also has been found to improve the co-planarity of composite magnetic transducing heads.

Abstract: An encoding/decoding system for 1,7,2,3 codes employs an oscillator having a frequency f and dividers providing signals at frequencies equal to 1/3 f and 2/3 f. A code converter is responsive to the three signals to encode or decode data. A 3/2 frequency divider employs two D-type flip-flops, an OR gate and an AND gate arranged to respond to an input signal at a frequency f to derive an output signal at a frequency 2/3 f.

Abstract: A magnetoresistive sensor element having bottleneck shaped ends. The sensor element has a highly stable, single domain central region, which eliminates Barkhausen noise.

Abstract: A thin film magnetic recording head has a flux path in which during writing magnetic saturation occurs in the throat section of the leading pole rather than in the trailing pole. This keeps the stray magnetic fields generated in the area where the saturation occurs during writing from distorting the just-recorded data pattern in the medium, since the leading pole is spaced sufficiently far from the data pattern as it is created adjacent the trailing pole. Preferably, this is accomplished by making a cross section area of the flux path in the leading pole throat section physically smaller than the minimum cross section area in the remainder of the leading pole or in the trailing pole and is throat section.

Abstract: In an optical recording system, a media disk for writing information has a plurality of information tracks with preformatted clock location indications written on the tracks. Writing is accomplished by making a written indication at a predetermined location between preformatted clock locations where the predetermined location is representative of the particular data to be written. Proper location of the preformatted clock location indicia on adjacent tracks provides for proper track crossing information when track addressing occurs as well as proper address location on particular tracks.