Digital Equipment Corporation

Other

Friedrich R Hertrich

Robert F Heidecker

Slobodan R Perera

James O Jacques

Richard D Cordano

In a multi-track digital recording medium, data blocks on different tracks are algebraically combined to generate an error correction code (ECC) stored in an ECC block on one of the tracks. Unrecoverable errors due to horizontal and vertical clustering of dropouts on magnetic tape, for example, are reduced by XOR-ing data blocks along a diagonal path traversing several tracks to form the ECC.

Stored data error correction system

A brushless DC motor having a number of armature poles which is neither a multiple nor a submultiple of the number of field poles, thereby providing a relatively high cogging-ripple frequency. The field pole faces, which are generally arcuate in cross-section, have centrally disposed depressions. These depressions reduce the torque exerted by the armature when pole boundaries of the armature pass by the centers of the field poles. This reduces both torque ripple and cogging ripple and it doubles the frequency of torque ripple.

Brushless DC motor

A self-cleaning head assembly characterized by one or more raised head islands with convex top surfaces and sloped sides, and designed to be used with a recording medium, such as a magnetic tape, which wraps each island. The machined radius of curvature of the top surface of the head island is not less than half the natural curvature of the tape, and the running radius of the head is approximately equal to the natural curvature of the medium. A steep angle of approach between tape and head provides cleaning action, while the small top surface reduces errors due to lift-off and provides superior magnetic contact.

Narrow contour head assembly

An armature for a DC motor includes a plurality of circumferentially spaced armature segments having salient poles with arcuate surfaces and air pockets formed within the poles adjacent to but not intersecting the surfaces, sized and located to reduce cogging due to variations in reluctance. The armature segments are preferably bridged by flux links carrying prewound electrical coils arranged in a circular path. Corresponding lamina in each armature segment are formed of a unitary stamping in which the segments are interconnected by removable flexible joints.

Armature for DC motor

The present system for joining tape leaders is comprised of an elongated member which has a finger like protrusion and a cam protrusion both of which are disposed close to one end thereof. The elongated member has an elongated slot at one end which fits over a stud and is further rotationally coupled to a crank so that the elongated member can pivot around said stud in a number of different positions in response to the crank being moved. The crank is rotationally coupled to a cam follower and the crank is further arranged to rotate about a stud.

Mechanism for joining tape leaders

The present system is comprised of an elongated member which has a finger like protrusion and a cam protrusion both of which are disposed close to one end thereof. The elongated member has an elongated slot at one end which fits over a stud and is further rotationally coupled to a crank so that the elongated member can pivot around said stud in a number of different positions in response to the crank being moved. The crank is rotationally coupled to a cam follower and the crank is further arranged to rotate about a stud. When a tape leader from a take up reel is to be joined to a tape leader from a supply reel, the elongated member is moved toward the tape leader from the take up reel and the finger like protrusion enters a first slot in the take up reel leader and moves that leader to an extended position whereat the cam protrusion cams a tab on the end of the take up reel leader away from the elongated member. The tab is formed to have a stem section. The supply reel leader which is extended has a locking slot therein which has a first section which fits over the tab. In response to said camming action, the elongated member is moved such that said cam protrusion cams said tab deeply into said locking slot and said tab becomes locked in a narrow section of said locking slot.

The present arrangement includes a first tape leader which can be readily and automatically coupled to a second tape leader. In a preferred embodiment the first tape leader is connected to be wound on a take up reel while the second tape leader is connected to a tape to be pulled from a supply reel. The first tape leader has one end formed into a mushroom like tab with a supporting stem. The second tape leader has a locking aperture at one end thereof which is proportioned so that a wide section thereof can fit over said mushroom like tab while a narrow section thereof will accept the stem but block passage of the mushroom tab therethrough. Accordingly when the tab is passed through the wide section and the leader is moved (pulled) toward the narrow section of the locking aperture, the tab and part of the stem become locked in the narrow section. Hence the leaders are locked, or buckled, to enable the first tape leader to pull the second leader. The first and second tape leaders each have a smoothing aperture therein which provides a means to accept the bumps created by buckling the tab into the locking aperture so that the wrapped around leaders are in a smooth configuration when pulling a tape.

Means for pulling tape from a reel

A transducer positioning system and a magnetic disk therefor for use in a disk drive unit of a data processing system. The magnetic disk contains plural servo sectors interposed between a plurality of circumferentially spaced data sectors. Each servo sector contains at least two sets of spaced servo blocks that include first and second asymmetrical, time-displaced, complementary servo information signals located in radially adjacent blocks. Respective sets of data track centerlines are aligned with the phase boundaries of an associated set of servo blocks in the servo sector. The disk drive unit includes a controller that selects one of the servo blocks and use a null detector to position a movable transducer over a data track centerline associated with the set of phase boundaries of the selected servo block. The controller additionally includes a track difference counter responsive to the null detector thereby to count zero crossings of the phase boundaries during movement of the transducer for indicating the displacement between the movable transducer and the desired data track in the data sector and for controlling the movement of the transducer.

Transducer positioning system and data disk therefor

A velocity transducer for converting linear mechanical motion to an electrical signal. A stationary permanent magnet is supported within and spaced from an iron pole piece assembly which forms a closed path around the magnet. The pole piece assembly has a pair of linear pole piece segments which extend in parallel on opposite sides of the magnet, spaced apart from the north and south pole faces of the magnet, respectively. A moveable (i.e. slideable) coil is wound around each such linear pole piece. The two coils are series-connected and oppositely wound with respect to the flux produced by the magnet. Noise signals induced in the coils subtract from each other and substantially cancel, but motion-related signals add.

Differential linear velocity transducer

A transducer positioning system for a rotating magnetic disk memory unit in which servo positioning information is interspersed with data. The disk comprises concentric data tracks individually divided into spaced data sectors. Two sets of radially extending blocks of servo information are recorded between each pair of adjacent data sectors. Adjacent blocks in each set produce asymmetrical pulse trains that are the time-displaced complements of each other. A first set of blocks are positioned radially so that their boundaries lie on the data track centerlines. Each block in the second set is aligned with a data track. A transducer positioning device utilizes the first blocks of information to maintain the transducer in alignment with a track and the first and second blocks of information in moving the transducer from one track to another.

Transducer positioning system for rotating disk drive units

A sector formatting and record addressing scheme and associated electronic recording and detection control systems for a removable cartridge disc used in a magnetic information storage unit. Indelible sector mark and record address/format information are electronically pre-recorded on the disc at the factory using a high precision cartridge writer. This cartridge writer phase-locks the recording clock to a magnetically recorded clocking disc rotating on the same shaft as the disc via an associated position transducer to write an exact number of bytes on each track having a precise physical relationship to each other. Separate recording clocks having a wide bit-frequency spectral separation are used to write sector mark and address/format data to provide maximum sector detection reliability. The cartridge writer control system computes the optimum length of sector code for the customer-specified record size. The sector format arrangement is designed to facilitate address checking and data recovery in the user environment with a minimum of control complexity.

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Boulder, CO, United States of America

Friedrich R Hertrich