Browse Prior Art Database

Combination Centerpole/Rail/Shorted Turn

IP.com Disclosure Number: IPCOM000116694D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 4 page(s) / 77K

Publishing Venue

IBM

Related People

Hirasaka, Y: AUTHOR [+4]

Abstract

To increase optical drive's seek times, several parameters can be adjusted including the actuator's moving mass, G's/amp, friction, and the applied current's rise time through the actuator's coils. Current IBM* optical drive design has reduced mass by combining the VCM's centerpole with the bearing rails as shown in Fig. 1. As seen in Fig. 1, the rail acts both as the centerpole for the magnetic circuit and the surface which the carriage's ball bearings roll on. In other words, the magnetic flux travels through the rails which also act as ball bearing surfaces. To attain both a good magnetic circuit, and a good bearing surface, hard chrome is coated over a softer, more magnetic soft iron, as shown in Fig. 2.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 79% of the total text.

Combination Centerpole/Rail/Shorted Turn

      To increase optical drive's seek times, several parameters can
be adjusted including the actuator's moving mass, G's/amp, friction,
and the applied current's rise time through the actuator's coils.
Current IBM* optical drive design has reduced mass by combining the
VCM's centerpole with the bearing rails as shown in Fig. 1.  As seen
in Fig. 1, the rail acts both as the centerpole for the magnetic
circuit and the surface which the carriage's ball bearings roll on.
In other words, the magnetic flux travels through the rails which
also act as ball bearing surfaces.  To attain both a good magnetic
circuit, and a good bearing surface, hard chrome is coated over a
softer, more magnetic soft iron, as shown in Fig. 2.

      Most actuator designs which attain high seek rates use a
technique called a 'shorted turn', which is an industry practice.
This is done most commonly by completely circling the centerpole with
a copper sleeve.  However, with the half-high design, if a copper
sleeve was placed over the rails (typical practice), then the ball
bearings would quickly cause wear problems as they crossed back and
forth along the copper sleeve.

      The solution to this problem is by making a three piece rail
with an inner material composed of soft iron (form magnetics), a
middle section made of copper (for better rise time), and a outer
material made from hard chrome (for bearing wear).  Figs. 3 and 4
show a rail compos...