A magnet structure includes first and second magnet units. The first magnet unit is provided with a first magnet fixing section that includes a first surface and a first magnet having a first polarity on the first surface's side. The second magnet unit is provided with a second magnet fixing section that includes a second surface and a second magnet having a second polarity on the second surface's side, the second polarity being an opposite polarity to the first polarity. The first and second surfaces are located next to one another on the same plane to form a magnetic attachment surface which is magnetically attached to a magnetically-attached object. The second magnet unit is supported by the first magnet unit so as to move in a predetermined range.

According to one embodiment, a magnetic disk device includes a disk medium which has a first region, a second region, and a redundant third region, and a control circuitry. The first region is a region to which first data received from a host is written. The second region is a region to which the first data is temporarily written before the first data is written to the first region. The control circuitry executes defect detection to the first region. Upon detecting a defect, the control circuitry substitutes a first location having the defect in the first region with a second location in the third region. Depending on a total size of free regions of the third region, the control circuitry reallocates a fourth region from the second region to the third region. The fourth region is part or all of the second region.

According to one embodiment, a magnetic disk device includes a disk medium which has a first region, a second region, and a redundant third region, and a control circuitry. The first region is a region to which first data received from a host is written. The second region is a region to which the first data is temporarily written before the first data is written to the first region. The control circuitry executes defect detection to the first region. Upon detecting a defect, the control circuitry substitutes a first location having the defect in the first region with a second location in the third region. Depending on a total size of free regions of the third region, the control circuitry reallocates a fourth region from the second region to the third region. The fourth region is part or all of the second region.

An apparatus for changing a record comprising a record changing fork comprising first and second spaced apart tines arranged in a record plane and extending from a fork base to a fork mouth, each tine comprising a groove extending from the fork mouth at least part way to the fork base, the grooves being arranged to hold a record therebetween in the record plane; at least one tine comprising a resiliently deformable record gate, the record gate being adapted to prevent sliding of a record in the grooves past the record gate unless the record is slid with a force exceeding a threshold force; at least one shelf adapted to support a record, the width of the shelf being less than the separation between the tines; and, a control mechanism connected to the record changing fork.

An apparatus for changing a record comprising a record changing fork comprising first and second spaced apart tines arranged in a record plane and extending from a fork base to a fork mouth, each tine comprising a groove extending from the fork mouth at least part way to the fork base, the grooves being arranged to hold a record therebetween in the record plane; at least one tine comprising a resiliently deformable record gate, the record gate being adapted to prevent sliding of a record in the grooves past the record gate unless the record is slid with a force exceeding a threshold force; at least one shelf adapted to support a record, the width of the shelf being less than the separation between the tines; and, a control mechanism connected to the record changing fork.

According to one embodiment, a disk clamp includes a disk-shaped main body including a central axis line, an annular mounting groove provided in a first surface of the main body, in which a wire for unbalance adjustment is mountable, a plurality of through-holes formed through the main body and spaced apart from each other equally in a circumferential direction around the central axis line, through each of which a fixing screw is insertable, and a plurality of female threaded holes formed on the first surface of the main body and spaced apart from each other equally in the circumferential direction, through each of which an adjustment screw for balancing adjustment is screwable.

A conveying roller position manipulation mechanism moves the position of a conveying roller between a first roller position where the conveying roller contacts an optical disc and a second roller position where the conveying roller is separated from the optical disc. A centering mechanism aligns the center of the optical disc with the position of a spindle motor. A chucking pulley operation mechanism manipulates the position of a chucking pulley configured to fix the optical disc to the spindle motor. The conveying roller position manipulation mechanism includes a rotary arm configured to move in response to a collision with the optical disc that approaches the position of the spindle motor, and at least one of the centering mechanism and the chucking pulley operation mechanism includes a member coupled to the rotary arm.

A conveying roller position manipulation mechanism moves the position of a conveying roller between a first roller position where the conveying roller contacts an optical disc and a second roller position where the conveying roller is separated from the optical disc. A centering mechanism aligns the center of the optical disc with the position of a spindle motor. A chucking pulley operation mechanism manipulates the position of a chucking pulley configured to fix the optical disc to the spindle motor. The conveying roller position manipulation mechanism includes a rotary arm configured to move in response to a collision with the optical disc that approaches the position of the spindle motor, and at least one of the centering mechanism and the chucking pulley operation mechanism includes a member coupled to the rotary arm.

A disk drive assembly including a spindle motor including a hub and a central axis, at least one disk disk having a central opening positioned on the hub and concentric about the central axis, an annular ring member concentric about the central axis, wherein a first portion of the annular ring member is in contact with an outer surface of a top disk of the disk stack, and a disk clamp ring screw adjacent to and in contact with a second portion of the annular ring member, wherein the disk clamp ring screw provides a clamping force to at least partially compress the annular ring member toward the top disk of the disk stack.

A disk drive assembly including a spindle motor including a hub and a central axis, at least one disk disk having a central opening positioned on the hub and concentric about the central axis, an annular ring member concentric about the central axis, wherein a first portion of the annular ring member is in contact with an outer surface of a top disk of the disk stack, and a disk clamp ring screw adjacent to and in contact with a second portion of the annular ring member, wherein the disk clamp ring screw provides a clamping force to at least partially compress the annular ring member toward the top disk of the disk stack.