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Latch performance enhancement by concentrating the VCM's magnetic stray field

IP.com Disclosure Number: IPCOM000015220D
Original Publication Date: 2001-Nov-28
Included in the Prior Art Database: 2003-Jun-20
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Abstract

The inertial latch prevents the heads of a nonoperating HDD from being inadvertently loaded onto stationary disks after experiencing a rotary shock. During a rotary shock the inertial latch rotates toward the actuators, hooks on the latch engages hooks on the actuators stopping further actuator rotation. Shortly after capture of the actuators is complete the latch must rotate away from the actuators to release them and it must return to the home position. The home position allows the actuators to rotate freely during normal operating conditions. The latch return force comes from the VCM’s stray magnetic field pulling on a steel sphere embedded in the latch. This force pulls it toward the magnet. A latch may get stuck in the ‘capture’ position if there is not enough torque exerted on it by the dual VCM stray field to return it to the home position. When the latch is stuck it prevents the actuators from rotating and loading heads onto the disk during normal operating conditions. The steel center pole piece of a dual (stacked) actuator VCM has an opening in it that concentrates the stray magnetic field from the magnet, as is shown in Figure 1. The concentrated magnetic flux attracts a steel ball (or other shape) in the inertial latch so that it returns to the home (or open) position. Without the higher flux density either a larger, heavier steel ball or a thicker, stronger magnet would be required. The objects of the invention are to increase the return torque acting on the latch without increasing the inertia or mass of the latch and to stay within the dimensional constraints imposed by the HDD form factor. 1

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Latch performance enhancement by concentrating the VCM's magnetic stray field

The inertial latch prevents the heads of a nonoperating HDD from being inadvertently loaded onto stationary disks after experiencing a rotary shock. During a rotary shock the inertial latch rotates toward the actuators, hooks on the latch engages hooks on the actuators stopping further actuator rotation. Shortly after capture of the actuators is complete the latch must rotate away from the actuators to release them and it must return to the home position. The home position allows the actuators to rotate freely during normal operating conditions. The latch return force comes from the VCM's stray magnetic field pulling on a steel sphere embedded in the latch. This force pulls it toward the magnet. A latch may get stuck in the 'capture' position if there is not enough torque exerted on it by the dual VCM stray field to return it to the home position.

When the latch is stuck it prevents the actuators from rotating and loading heads onto the disk during normal operating conditions.

The steel center pole piece of a dual (stacked) actuator VCM has an opening in it that concentrates the stray magnetic field from the magnet, as is shown in Figure 1. The concentrated magnetic flux attracts a steel ball (or other shape) in the inertial latch so that it returns to the home (or open) position. Without the higher flux density either a larger, heavier steel ball or a thicker, stronger magnet would be...